Interval (music)

For albums named Intervals, see Interval (disambiguation).
Melodic and harmonic intervals.  Play 

In music theory, an interval is the difference between two pitches.[1] An interval may be described as horizontal, linear, or melodic if it refers to successively sounding tones, such as two adjacent pitches in a melody, and vertical or harmonic if it pertains to simultaneously sounding tones, such as in a chord.[2][3]

In Western music, intervals are most commonly differences between notes of a diatonic scale. The smallest of these intervals is a semitone. Intervals smaller than a semitone are called microtones. They can be formed using the notes of various kinds of non-diatonic scales. Some of the very smallest ones are called commas, and describe small discrepancies, observed in some tuning systems, between enharmonically equivalent notes such as C♯ and D♭. Intervals can be arbitrarily small, and even imperceptible to the human ear.

In physical terms, an interval is the ratio between two sonic frequencies. For example, any two notes an octave apart have a frequency ratio of 2:1. This means that successive increments of pitch by the same interval result in an exponential increase of frequency, even though the human ear perceives this as a linear increase in pitch. For this reason, intervals are often measured in cents, a unit derived from the logarithm of the frequency ratio.

In Western music theory, the most common naming scheme for intervals describes two properties of the interval: the quality (perfect, major, minor, augmented, diminished) and number (unison, second, third, etc.). Examples include the minor third or perfect fifth. These names describe not only the difference in semitones between the upper and lower notes, but also how the interval is spelled. The importance of spelling stems from the historical practice of differentiating the frequency ratios of enharmonic intervals such as G–G♯ and G–A♭.[4]

Size

Example: Perfect octave on C in equal temperament and just intonation: 2/1 = 1200 cents.  Play 

The size of an interval (also known as its width or height) can be represented using two alternative and equivalently valid methods, each appropriate to a different context: frequency ratios or cents.

Frequency ratios

Main article: Interval ratio

The size of an interval between two notes may be measured by the ratio of their frequencies. When a musical instrument is tuned using a just intonation tuning system, the size of the main intervals can be expressed by small-integer ratios, such as 1:1 (unison), 2:1 (octave), 3:2 (perfect fifth), 4:3 (perfect fourth), 5:4 (major third), 6:5 (minor third). Intervals with small-integer ratios are often called just intervals, or pure intervals.

Most commonly, however, musical instruments are nowadays tuned using a different tuning system, called 12-tone equal temperament. As a consequence, the size of most equal-tempered intervals cannot be expressed by small-integer ratios, although it is very close to the size of the corresponding just intervals. For instance, an equal-tempered fifth has a frequency ratio of 27/12:1, approximately equal to 1.498:1, or 2.997:2 (very close to 3:2). For a comparison between the size of intervals in different tuning systems, see section Size in different tuning systems.

Cents

Main article: Cent (music)

The standard system for comparing interval sizes is with cents. The cent is a logarithmic unit of measurement. If frequency is expressed in a logarithmic scale, and along that scale the distance between a given frequency and its double (also called octave) is divided into 1200 equal parts, each of these parts is one cent. In twelve-tone equal temperament (12-TET), a tuning system in which all semitones have the same size, the size of one semitone is exactly 100 cents. Hence, in 12-TET the cent can be also defined as one hundredth of a semitone.

Mathematically, the size in cents of the interval from frequency f1 to frequency f2 is

n = 1200 \cdot \log_2 \left( \frac{f_2}{f_1} \right).

Main intervals

The table shows the most widely used conventional names for the intervals between the notes of a chromatic scale. A perfect unison (also known as perfect prime)[5] is an interval formed by two identical notes. Its size is zero cents. A semitone is any interval between two adjacent notes in a chromatic scale, a whole tone is an interval spanning two semitones (for example, a major second), and a tritone is an interval spanning three tones, or six semitones (for example, an augmented fourth).[6] Rarely, the term ditone is also used to indicate an interval spanning two whole tones (for example, a major third), or more strictly as a synonym of major third.

Intervals with different names may span the same number of semitones, and may even have the same width. For instance, the interval from D to F♯ is a major third, while that from D to G♭ is a diminished fourth. However, they both span 4 semitones. If the instrument is tuned so that the 12 notes of the chromatic scale are equally spaced (as in equal temperament), these intervals will also have the same width. Namely, all semitones will have a width of 100 cents, and all intervals spanning 4 semitones will be 400 cents wide.

The names listed here cannot be determined by counting semitones alone. The rules to determine them are explained below. Other names, determined with different naming conventions, are listed in a separate section. Intervals smaller than one semitone (commas or microtones) and larger than one octave (compound intervals) are introduced below.

Number of
semitones		 Minor, major,
or perfect intervals 		Short Augmented or
diminished intervals 		Short Widely used
alternative names 		Short Audio
0 Perfect unison[5][7] P1 Diminished second d2  Play 
1 Minor second m2 Augmented unison[5][7] A1 Semitone,[8] half tone, half step S  Play 
2 Major second M2 Diminished third d3 Tone, whole tone, whole step T  Play 
3 Minor third m3 Augmented second A2  Play 
4 Major third M3 Diminished fourth d4  Play 
5 Perfect fourth P4 Augmented third A3  Play 
6 Diminished fifth d5 Tritone[6] TT  Play 
Augmented fourth A4
7 Perfect fifth P5 Diminished sixth d6  Play 
8 Minor sixth m6 Augmented fifth A5  Play 
9 Major sixth M6 Diminished seventh d7  Play 
10 Minor seventh m7 Augmented sixth A6  Play 
11 Major seventh M7 Diminished octave d8  Play 
12 Perfect octave P8 Augmented seventh A7  Play 

Interval number and quality

Main intervals from C.  Play 

In Western music theory, an interval is named according to its number (also called diatonic number) and quality. For instance, major third (or M3) is an interval name, in which the term major (M) describes the quality of the interval, and third (3) indicates its number.

Number

Staff, with staff positions indicated.
Fifth from C to G in the A♭ major scale.

The number of an interval is the number of letter names it encompasses or staff positions it encompasses. Both lines and spaces (see figure) are counted, including the positions of both notes forming the interval. For instance, the interval C–G is a fifth (denoted P5) because the notes from C to the G above it encompass five letter names (C, D, E, F, G) and occupy five consecutive staff positions, including the positions of C and G. The table and the figure above show intervals with numbers ranging from 1 (e.g., P1) to 8 (e.g., P8). Intervals with larger numbers are called compound intervals.

There is a one-to-one correspondence between staff positions and diatonic-scale degrees (the notes of a diatonic scale).[9] This means that interval numbers can be also determined by counting diatonic scale degrees, rather than staff positions, provided that the two notes which form the interval are drawn from a diatonic scale. Namely, C–G is a fifth because in any diatonic scale that contains C and G, the sequence from C to G includes five notes. For instance, in the A♭-major diatonic scale, the five notes are C–D♭–E♭–F–G (see figure). This is not true for all kinds of scales. For instance, in a chromatic scale, the notes from C to G are eight (C–C♯–D–D♯–E–F–F♯–G). This is the reason interval numbers are also called diatonic numbers, and this convention is called diatonic numbering.

If one adds any accidentals to the notes that form an interval, by definition the notes do not change their staff positions. As a consequence, any interval has the same interval number as the corresponding natural interval, formed by the same notes without accidentals. For instance, the intervals C–G♯ (spanning 8 semitones) and C♯–G (spanning 6 semitones) are fifths, like the corresponding natural interval C–G (7 semitones).

Notice that interval numbers represent an inclusive count of encompassed staff positions or note names, not the difference between the endpoints. In other words, start counting the lower pitch as one, not zero. For that reason, the interval C–C, a perfect unison, is called a prime (meaning "1"), even though there's no difference between the endpoints. Continuing, the interval C–D is a second, but D is only one staff position, or diatonic-scale degree, above C. Similarly, C–E is a third, but E is only two staff positions above C, and so on. As a consequence, joining two intervals always yields an interval number one less than their sum. For instance, the intervals C–E and E–G are thirds, but joined together they form a fifth (C–G), not a sixth. Similarly, a stack of three thirds, such as C–E, E–G, and G–B, is a seventh (C–B), not a ninth.

Read the Compound intervals section to determine the diatonic numbers of a intervals larger than an octave.

Quality

The name of any interval is further qualified using the terms perfect (P), major (M), minor (m), augmented (A), and diminished (d). This is called its interval quality. It is possible to have doubly diminished and doubly augmented intervals, but these are quite rare, as they occur only in chromatic contexts. The quality of a compound interval is the quality of the simple interval on which it is based.

Perfect
Perfect intervals on C.  PU ,  P4 ,  P5 ,  P8 .

Perfect intervals are so-called because they were traditionally considered perfectly consonant,[10] although in Western classical music the perfect fourth was sometimes regarded as a less than perfect consonance, when its function was contrapuntal. Conversely, minor, major, augmented or diminished intervals are typically considered to be less consonant, and were traditionally classified as mediocre consonances, imperfect consonances, or dissonances.[10]

Within a diatonic scale[9] all unisons (P1) and octaves (P8) are perfect. Most fourths and fifths are also perfect (P4 and P5), with five and seven semitones respectively. There's one occurrence of a fourth and a fifth which are not perfect, as they both span six semitones: an augmented fourth (A4), and its inversion, a diminished fifth (d5). For instance, in a C-major scale, the A4 is between F and B, and the d5 is between B and F (see table).

By definition, the inversion of a perfect interval is also perfect. Since the inversion does not change the pitch of the two notes, it hardly affects their level of consonance (matching of their harmonics). Conversely, other kinds of intervals have the opposite quality with respect to their inversion. The inversion of a major interval is a minor interval, the inversion of an augmented interval is a diminished interval.

Major and minor
Major and minor intervals on C.  m2 ,  M2 ,  m3 ,  M3 ,  m6 ,  M6 ,  m7 ,  M7 

As shown in the table, a diatonic scale[9] defines seven intervals for each interval number, each starting from a different note (seven unisons, seven seconds, etc.). The intervals formed by the notes of a diatonic scale are called diatonic. Except for unisons and octaves, the diatonic intervals with a given interval number always occur in two sizes, which differ by one semitone. For example, six of the fifths span seven semitones. The other one spans six semitones. Four of the thirds span three semitones, the others four. If one of the two versions is a perfect interval, the other is called either diminished (i.e. narrowed by one semitone) or augmented (i.e. widened by one semitone). Otherwise, the larger version is called major, the smaller one minor. For instance, since a 7-semitone fifth is a perfect interval (P5), the 6-semitone fifth is called "diminished fifth" (d5). Conversely, since neither kind of third is perfect, the larger one is called "major third" (M3), the smaller one "minor third" (m3).

Within a diatonic scale,[9] unisons and octaves are always qualified as perfect, fourths as either perfect or augmented, fifths as perfect or diminished, and all the other intervals (seconds, thirds, sixths, sevenths) as major or minor.

Augmented and diminished
Augmented and diminished intervals on C.  d2 ,  A2 ,  d3 ,  A3 ,  d4 ,  A4 ,  d5 ,  A5 ,  d6 ,  A6 ,  d7 ,  A7 ,  d8 ,  A8 

Augmented intervals are wider by one semitone than perfect or major intervals, while having the same interval number (i.e., encompassing the same number of staff positions). Diminished intervals are narrower by one semitone than perfect or minor intervals of the same interval number. For instance, an augmented third such as C–E♯ spans five semitones, exceeding a major third (C–E) by one semitone, while a diminished third such as C♯–E♭ spans two semitones, falling short of a minor third (C–E♭) by one semitone.

The augmented fourth (A4) and the diminished fifth (d5) are the only augmented and diminished intervals that appear in diatonic scales[9] (see table).

Example

Neither the number, nor the quality of an interval can be determined by counting semitones alone. As explained above, the number of staff positions must be taken into account as well.

For example, as shown in the table below, there are four semitones between A♭ and B♯, between A and C♯, between A and D♭, and between A♯ and E, but

Number
of semitones 		Interval name Staff positions
1 2 3 4 5
4 doubly augmented second A♭ B♯    
4 major third A   C♯  
4 diminished fourth A     D♭
4 triply diminished fifth A♯       E

Shorthand notation

Intervals are often abbreviated with a P for perfect, m for minor, M for major, d for diminished, A for augmented, followed by the interval number. The indication M and P are often omitted. The octave is P8, and a unison is usually referred to simply as "a unison" but can be labeled P1. The tritone, an augmented fourth or diminished fifth is often TT. The interval qualities may be also abbreviated with perf, min, maj, dim, aug. Examples:

Inversion

Main article: Inversion (music)
Major 13th (compound Major 6th) inverts to a minor 3rd by moving the bottom note up two octaves, the top note down two octaves, or both notes one octave

A simple interval (i.e., an interval smaller than or equal to an octave) may be inverted by raising the lower pitch an octave, or lowering the upper pitch an octave. For example, the fourth from a lower C to a higher F may be inverted to make a fifth, from a lower F to a higher C.

There are two rules to determine the number and quality of the inversion of any simple interval:[11]

  1. The interval number and the number of its inversion always add up to nine (4 + 5 = 9, in the example just given).
  2. The inversion of a major interval is a minor interval, and vice versa; the inversion of a perfect interval is also perfect; the inversion of an augmented interval is a diminished interval, and vice versa; the inversion of a doubly augmented interval is a doubly diminished interval, and vice versa.

For example, the interval from C to the E♭ above it is a minor third. By the two rules just given, the interval from E♭ to the C above it must be a major sixth.

Since compound intervals are larger than an octave, "the inversion of any compound interval is always the same as the inversion of the simple interval from which it is compounded."[12]

For intervals identified by their ratio, the inversion is determined by reversing the ratio and multiplying by 2. For example, the inversion of a 5:4 ratio is an 8:5 ratio.

For intervals identified by an integer number of semitones, the inversion is obtained by subtracting that number from 12.

Since an interval class is the lower number selected among the interval integer and its inversion, interval classes cannot be inverted.

Classification

Intervals can be described, classified, or compared with each other according to various criteria.

Melodic and harmonic intervals.  Play 

Melodic and harmonic

Main articles: Harmony and Melody

An interval can be described as

Diatonic and chromatic

In general,

Ascending and descending chromatic scale on C  Play .

The table above depicts the 56 diatonic intervals formed by the notes of the C major scale (a diatonic scale). Notice that these intervals, as well as any other diatonic interval, can be also formed by the notes of a chromatic scale.

The distinction between diatonic and chromatic intervals is controversial, as it is based on the definition of diatonic scale, which is variable in the literature. For example, the interval B–E♭ (a diminished fourth, occurring in the harmonic C-minor scale) is considered diatonic if the harmonic minor scales are considered diatonic as well.[13] Otherwise, it is considered chromatic. For further details, see the main article.

By a commonly used definition of diatonic scale[9] (which excludes the harmonic minor and melodic minor scales), all perfect, major and minor intervals are diatonic. Conversely, no augmented or diminished interval is diatonic, except for the augmented fourth and diminished fifth.

The A♭-major scale.  Play 

The distinction between diatonic and chromatic intervals may be also sensitive to context. The above-mentioned 56 intervals formed by the C-major scale are sometimes called diatonic to C major. All other intervals are called chromatic to C major. For instance, the perfect fifth A♭–E♭ is chromatic to C major, because A♭ and E♭ are not contained in the C major scale. However, it is diatonic to others, such as the A♭ major scale.

Consonant and dissonant

Consonance and dissonance are relative terms that refer to the stability, or state of repose, of particular musical effects. Dissonant intervals are those that cause tension, and desire to be resolved to consonant intervals.

These terms are relative to the usage of different compositional styles.

All of the above analyses refer to vertical (simultaneous) intervals.

Simple and compound

Simple and compound major third.  Play 

A simple interval is an interval spanning at most one octave (see Main intervals above). Intervals spanning more than one octave are called compound intervals, as they can be obtained by adding one or more octaves to a simple interval (see below for details).[17]

Steps and skips

Main article: Steps and skips

Linear (melodic) intervals may be described as steps or skips. A step, or conjunct motion,[18] is a linear interval between two consecutive notes of a scale. Any larger interval is called a skip (also called a leap), or disjunct motion.[18] In the diatonic scale,[9] a step is either a minor second (sometimes also called half step) or major second (sometimes also called whole step), with all intervals of a minor third or larger being skips.

For example, C to D (major second) is a step, whereas C to E (major third) is a skip.

More generally, a step is a smaller or narrower interval in a musical line, and a skip is a wider or larger interval, with the categorization of intervals into steps and skips is determined by the tuning system and the pitch space used.

Melodic motion in which the interval between any two consecutive pitches is no more than a step, or, less strictly, where skips are rare, is called stepwise or conjunct melodic motion, as opposed to skipwise or disjunct melodic motions, characterized by frequent skips.

Enharmonic intervals

Main article: Enharmonic
Enharmonic tritones: A4 = d5 on C  Play .

Two intervals are considered to be enharmonic, or enharmonically equivalent, if they both contain the same pitches spelled in different ways; that is, if the notes in the two intervals are themselves enharmonically equivalent. Enharmonic intervals span the same number of semitones.

For example, the four intervals listed in the table below are all enharmonically equivalent, because the notes F♯ and G♭ indicate the same pitch, and the same is true for A♯ and B♭. All these intervals span four semitones.

Number
of semitones 		Interval name Staff positions
1 2 3 4
4 major third F♯   A♯  
4 major third   G♭   B♭
4 diminished fourth F♯     B♭
4 doubly augmented second   G♭ A♯  

When played on a piano keyboard, these intervals are indistinguishable as they are all played with the same two keys, but in a musical context the diatonic function of the notes incorporated is very different.

Minute intervals

Pythagorean comma on C.  Play . The note depicted as lower on the staff (B♯+++) is slightly higher in pitch (than C♮).
Main articles: Comma (music) and Microtone

There are also a number of minute intervals not found in the chromatic scale or labeled with a diatonic function, which have names of their own. They may be described as microtones, and some of them can be also classified as commas, as they describe small discrepancies, observed in some tuning systems, between enharmonically equivalent notes. In the following list, the interval sizes in cents are approximate.

Compound intervals

Simple and compound major third.  Play 

A compound interval is an interval spanning more than one octave.[17] Conversely, intervals spanning at most one octave are called simple intervals (see Main intervals above).

In general, a compound interval may be defined by a sequence or "stack" of two or more simple intervals of any kind. For instance, a major tenth (two staff positions above one octave), also called compound major third, spans one octave plus one major third.

Any compound interval can be always decomposed into one or more octaves plus one simple interval. For instance, a major seventeenth can be decomposed into two octaves and one major third, and this is the reason why it is called a compound major third, even when it is built by adding up four fifths.

The diatonic number DNc of a compound interval formed from n simple intervals with diatonic numbers DN1, DN2, ..., DNn, is determined by:

DN_c = 1 + (DN_1 - 1) + (DN_2 - 1) + ... + (DN_n - 1), \

which can also be written as:

DN_c = DN_1 + DN_2 + ... + DN_n - (n - 1), \

The quality of a compound interval is determined by the quality of the simple interval on which it is based. For instance, a compound major third is a major tenth (1+(8–1)+(3–1) = 10), or a major seventeenth (1+(8–1)+(8–1)+(3–1) = 17), and a compound perfect fifth is a perfect twelfth (1+(8–1)+(5–1) = 12) or a perfect nineteenth (1+(8–1)+(8–1)+(5–1) = 19). Notice that two octaves are a fifteenth, not a sixteenth (1+(8–1)+(8–1) = 15). Similarly, three octaves are a twenty-second (1+3*(8–1) = 22), and so on.

Main compound intervals

Number of
semitones		 Minor, major,
or perfect intervals 		Short Augmented or
diminished intervals 		Short
12 Diminished ninth d9
13 Minor ninth m9 Augmented octave A8
14 Major ninth M9 Diminished tenth d10
15 Minor tenth m10 Augmented ninth A9
16 Major tenth M10 Diminished eleventh d11
17 Perfect eleventh P11 Augmented tenth A10
18 Diminished twelfth d12
Augmented eleventh A11
19 Perfect twelfth or Tritave P12 Diminished thirteenth d13
20 Minor thirteenth m13 Augmented twelfth A12
21 Major thirteenth M13 Diminished fourteenth d14
22 Minor fourteenth m14 Augmented thirteenth A13
23 Major fourteenth M14 Diminished fifteenth d15
24 Perfect fifteenth or Double octave P15 Augmented fourteenth A14
25 Augmented fifteenth A15

It is also worth mentioning here the major seventeenth (28 semitones), an interval larger than two octaves which can be considered a multiple of a perfect fifth (7 semitones) as it can be decomposed into four perfect fifths (7 * 4 = 28 semitones), or two octaves plus a major third (12 + 12 + 4 = 28 semitones). Intervals larger than a major seventeenth seldom need to be spoken of, most often being referred to by their compound names, for example "two octaves plus a fifth"[19] rather than "a 19th".

Intervals in chords

Chords are sets of three or more notes. They are typically defined as the combination of intervals starting from a common note called the root of the chord. For instance a major triad is a chord containing three notes defined by the root and two intervals (major third and perfect fifth). Sometimes even a single interval (dyad) is considered to be a chord.[20] Chords are classified based on the quality and number of the intervals which define them.

Chord qualities and interval qualities

The main chord qualities are: major, minor, augmented, diminished, half-diminished, and dominant. The symbols used for chord quality are similar to those used for interval quality (see above). In addition, + or aug is used for augmented, ° or dim for diminished, ø for half diminished, and dom for dominant (the symbol − alone is not used for diminished).

Deducing component intervals from chord names and symbols

The main rules to decode chord names or symbols are summarized below. Further details are given at Rules to decode chord names and symbols.

  1. For 3-note chords (triads), major or minor always refer to the interval of the third above the root note, while augmented and diminished always refer to the interval of the fifth above root. The same is true for the corresponding symbols (e.g., Cm means Cm3, and C+ means C+5). Thus, the terms third and fifth and the corresponding symbols 3 and 5 are typically omitted. This rule can be generalized to all kinds of chords,[21] provided the above-mentioned qualities appear immediately after the root note, or at the beginning of the chord name or symbol. For instance, in the chord symbols Cm and Cm7, m refers to the interval m3, and 3 is omitted. When these qualities do not appear immediately after the root note, or at the beginning of the name or symbol, they should be considered interval qualities, rather than chord qualities. For instance, in Cm/M7 (minor major seventh chord), m is the chord quality and refers to the m3 interval, while M refers to the M7 interval. When the number of an extra interval is specified immediately after chord quality, the quality of that interval may coincide with chord quality (e.g., CM7 = CM/M7). However, this is not always true (e.g., Cm6 = Cm/M6, C+7 = C+/m7, CM11 = CM/P11).[21] See main article for further details.
  2. Without contrary information, a major third interval and a perfect fifth interval (major triad) are implied. For instance, a C chord is a C major triad, and the name C minor seventh (Cm7) implies a minor 3rd by rule 1, a perfect 5th by this rule, and a minor 7th by definition (see below). This rule has one exception (see next rule).
  3. When the fifth interval is diminished, the third must be minor.[22] This rule overrides rule 2. For instance, Cdim7 implies a diminished 5th by rule 1, a minor 3rd by this rule, and a diminished 7th by definition (see below).
  4. Names and symbols which contain only a plain interval number (e.g., “Seventh chord”) or the chord root and a number (e.g., “C seventh”, or C7) are interpreted as follows:
    • If the number is 2, 4, 6, etc., the chord is a major added tone chord (e.g., C6 = CM6 = Cadd6) and contains, together with the implied major triad, an extra major 2nd, perfect 4th, or major 6th (see names and symbols for added tone chords).
    • If the number is 7, 9, 11, 13, etc., the chord is dominant (e.g., C7 = Cdom7) and contains, together with the implied major triad, one or more of the following extra intervals: minor 7th, major 9th, perfect 11th, and major 13th (see names and symbols for seventh and extended chords).
    • If the number is 5, the chord (technically not a chord in the traditional sense, but a dyad) is a power chord. Only the root, a perfect fifth and usually an octave are played.

The table shows the intervals contained in some of the main chords (component intervals), and some of the symbols used to denote them. The interval qualities or numbers in boldface font can be deduced from chord name or symbol by applying rule 1. In symbol examples, C is used as chord root.

Main chords Component intervals
Name Symbol examples Third Fifth Seventh
Major triad C maj3 perf5
CM, or Cmaj maj3 perf5
Minor triad Cm, or Cmin min3 perf5
Augmented triad C+, or Caug maj3 aug5
Diminished triad C°, or Cdim min3 dim5
Dominant seventh chord C7, or Cdom7 maj3 perf5 min7
Minor seventh chord Cm7, or Cmin7 min3 perf5 min7
Major seventh chord CM7, or Cmaj7 maj3 perf5 maj7
Augmented seventh chord C+7, Caug7,
C7♯5, or C7aug5 		maj3 aug5 min7
Diminished seventh chord C°7, or Cdim7 min3 dim5 dim7
Half-diminished seventh chord Cø7, Cm7♭5, or Cmin7dim5 min3 dim5 min7

Size of intervals used in different tuning systems

Number of
semitones		 Name 5-limit tuning
(pitch ratio)		 Comparison of interval width (in cents)
5-limit tuning Pythagorean
tuning		 1/4-comma
meantone		 Equal
temperament
0 Perfect unison 1:1 0 0 0 0
1 Minor second 16:15 112 90 117 100
2 Major second 9:8
10:9 		204
182 		204 193 200
3 Minor third 6:5
75:64
32:27 		316
(wolf) 275
294 		294
318 		310
(wolf) 269 		300
4 Major third 5:4
512:405
32:25
81:64 		386
406
(wolf) 427
408 		408
384 		386
(wolf) 427 		400
5 Perfect fourth 4:3
675:512
27:20 		498
478
520 		498
(wolf) 522 		503
(wolf) 462 		500
6 Augmented fourth
Diminished fifth 		45:32
64:45 		590
610 		612
588 		579
621 		600
7 Perfect fifth 3:2
40:27
1024:675 		702
680
722 		702
(wolf) 678 		697
(wolf) 738 		700
8 Minor sixth 8:5 814 792 814 800
9 Major sixth 5:3 884 906 890 900
10 Minor seventh 16:9
9:5 		996
1018 		996 1007 1000
11 Major seventh 15:8 1088 1110 1083 1100
12 Perfect octave 2:1 1200 1200 1200 1200

In this table, the interval widths used in four different tuning systems are compared. To facilitate comparison, just intervals as provided by 5-limit tuning (see symmetric scale n.1) are shown in bold font, and the values in cents are rounded to integers. Notice that in each of the non-equal tuning systems, by definition the width of each type of interval (including the semitone) changes depending on the note from which the interval starts. This is the price paid for seeking just intonation. However, for the sake of simplicity, for some types of interval the table shows only one value (the most often observed one).

In 1/4-comma meantone, by definition 11 perfect fifths have a size of approximately 697 cents (700−ε cents, where ε ≈ 3.42 cents); since the average size of the 12 fifths must equal exactly 700 cents (as in equal temperament), the other one must have a size of about 738 cents (700+11ε, the wolf fifth or diminished sixth); 8 major thirds have size about 386 cents (400−4ε), 4 have size about 427 cents (400+8ε, actually diminished fourths), and their average size is 400 cents. In short, similar differences in width are observed for all interval types, except for unisons and octaves, and they are all multiples of ε (the difference between the 1/4-comma meantone fifth and the average fifth). A more detailed analysis is provided at 1/4-comma meantone Size of intervals. Note that 1/4-comma meantone was designed to produce just major thirds, but only 8 of them are just (5:4, about 386 cents).

The Pythagorean tuning is characterized by smaller differences because they are multiples of a smaller ε (ε ≈ 1.96 cents, the difference between the Pythagorean fifth and the average fifth). Notice that here the fifth is wider than 700 cents, while in most meantone temperaments, including 1/4-comma meantone, it is tempered to a size smaller than 700. A more detailed analysis is provided at Pythagorean tuning#Size of intervals.

The 5-limit tuning system uses just tones and semitones as building blocks, rather than a stack of perfect fifths, and this leads to even more varied intervals throughout the scale (each kind of interval has three or four different sizes). A more detailed analysis is provided at 5-limit tuning#Size of intervals. Note that 5-limit tuning was designed to maximize the number of just intervals, but even in this system some intervals are not just (e.g., 3 fifths, 5 major thirds and 6 minor thirds are not just; also, 3 major and 3 minor thirds are wolf intervals).

The above-mentioned symmetric scale 1, defined in the 5-limit tuning system, is not the only method to obtain just intonation. It is possible to construct juster intervals or just intervals closer to the equal-tempered equivalents, but most of the ones listed above have been used historically in equivalent contexts. In particular, the asymmetric version of the 5-limit tuning scale provides a juster value for the minor seventh (9:5, rather than 16:9). Moreover, the tritone (augmented fourth or diminished fifth), could have other just ratios; for instance, 7:5 (about 583 cents) or 17:12 (about 603 cents) are possible alternatives for the augmented fourth (the latter is fairly common, as it is closer to the equal-tempered value of 600 cents). The 7:4 interval (about 969 cents), also known as the harmonic seventh, has been a contentious issue throughout the history of music theory; it is 31 cents flatter than an equal-tempered minor seventh. Some assert the 7:4 is one of the blue notes used in jazz. For further details about reference ratios, see 5-limit tuning#The justest ratios.

In the diatonic system, every interval has one or more enharmonic equivalents, such as augmented second for minor third.

Interval root

Intervals in the harmonic series.

Although intervals are usually designated in relation to their lower note, David Cope[16] and Hindemith[23] both suggest the concept of interval root. To determine an interval's root, one locates its nearest approximation in the harmonic series. The root of a perfect fourth, then, is its top note because it is an octave of the fundamental in the hypothetical harmonic series. The bottom note of every odd diatonically numbered intervals are the roots, as are the tops of all even numbered intervals. The root of a collection of intervals or a chord is thus determined by the interval root of its strongest interval.

As to its usefulness, Cope[16] provides the example of the final tonic chord of some popular music being traditionally analyzable as a "submediant six-five chord" (added sixth chords by popular terminology), or a first inversion seventh chord (possibly the dominant of the mediant V/iii). According the interval root of the strongest interval of the chord (in first inversion, CEGA), the perfect fifth (C–G), is the bottom C, the tonic.

Interval cycles

Main articles: Interval cycle and Identity (music)

Interval cycles, "unfold [i.e., repeat] a single recurrent interval in a series that closes with a return to the initial pitch class", and are notated by George Perle using the letter "C", for cycle, with an interval-class integer to distinguish the interval. Thus the diminished-seventh chord would be C3 and the augmented triad would be C4. A superscript may be added to distinguish between transpositions, using 0–11 to indicate the lowest pitch class in the cycle.[24]

Alternative interval naming conventions

As shown below, some of the above-mentioned intervals have alternative names, and some of them take a specific alternative name in Pythagorean tuning, five-limit tuning, or meantone temperament tuning systems such as quarter-comma meantone. All the intervals with prefix sesqui- are justly tuned, and their frequency ratio, shown in the table, is a superparticular number (or epimoric ratio). The same is true for the octave.

Typically, a comma is a diminished second, but this is not always true (for more details, see Alternative definitions of comma). For instance, in Pythagorean tuning the diminished second is a descending interval (524288:531441, or about -23.5 cents), and the Pythagorean comma is its opposite (531441:524288, or about 23.5 cents). 5-limit tuning defines four kinds of comma, three of which meet the definition of diminished second, and hence are listed in the table below. The fourth one, called syntonic comma (81:80) can neither be regarded as a diminished second, nor as its opposite. See Diminished seconds in 5-limit tuning for further details.

Number of
semitones		Generic names Specific names
Quality and number Other naming convention Pythagorean tuning 5-limit tuning 1/4-comma
meantone
Full Short
0 perfect unison
or perfect prime 		P1
diminished second d2 descending
Pythagorean comma
(524288:531441) 		lesser diesis (128:125)
diaschisma (2048:2025)
greater diesis (648:625)
1 minor second m2 semitone,
half tone,
half step 		diatonic semitone,
minor semitone 		limma (256:243)
augmented unison
or augmented prime		 A1 chromatic semitone,
major semitone 		apotome (2187:2048)
2 major second M2 tone, whole tone, whole step sesquioctavum (9:8)
3 minor third m3 sesquiquintum (6:5)
4 major third M3 sesquiquartum (5:4)
5 perfect fourth P4 sesquitertium (4:3)
6 diminished fifth d5 tritone[6]
augmented fourth A4
7 perfect fifth P5 sesquialterum (3:2)
12 perfect octave P8 duplex (2:1)

Additionally, some cultures around the world have their own names for intervals found in their music. For instance, 22 kinds of intervals, called shrutis, are canonically defined in Indian classical music.

Latin nomenclature

Up to the end of the 18th century, Latin was used as an official language throughout Europe for scientific and music textbooks. In music, many English terms are derived from Latin. For instance, semitone is from Latin semitonus.

The prefix semi- is typically used herein to mean "shorter", rather than "half".[25][26][27] Namely, a semitonus, semiditonus, semidiatessaron, semidiapente, semihexachordum, semiheptachordum, or semidiapason, is shorter by one semitone than the corresponding whole interval. For instance, a semiditonus (3 semitones, or about 300 cents) is not half of a ditonus (4 semitones, or about 400 cents), but a ditonus shortened by one semitone. Moreover, in Pythagorean tuning (the most commonly used tuning system up to the 16th century), a semitritonus (d5) is smaller than a tritonus (A4) by one Pythagorean comma (about a quarter of a semitone).

Number of
semitones		 Quality and number Short Latin
nomenclature
0 Perfect unison P1 unisonus
1 Minor second m2 semitonus
Augmented unison A1 unisonus superflua
2 Major second M2 tonus
Diminished third d3
3 Minor third m3 semiditonus
Augmented second A2 tonus superflua
4 Major third M3 ditonus
Diminished fourth d4 semidiatessaron
5 Perfect fourth P4 diatessaron
Augmented third A3 ditonus superflua
6 Diminished fifth d5 semidiapente, semitritonus
Augmented fourth A4 tritonus
7 Perfect fifth P5 diapente
Diminished sixth d6 semihexachordum
8 Minor sixth m6 hexachordum minus, semitonus maius cum diapente, tetratonus
Augmented fifth A5 diapente superflua
9 Major sixth M6 hexachordum maius, tonus cum diapente
Diminished seventh d7 semiheptachordum
10 Minor seventh m7 heptachordum minus, semiditonus cum diapente, pentatonus
Augmented sixth A6 hexachordum superflua
11 Major seventh M7 heptachordum maius, ditonus cum diapente
Diminished octave d8 semidiapason
12 Perfect octave P8 diapason
Augmented seventh A7 heptachordum superflua

Pitch-class intervals

In post-tonal or atonal theory, originally developed for equal-tempered European classical music written using the twelve-tone technique or serialism, integer notation is often used, most prominently in musical set theory. In this system, intervals are named according to the number of half steps, from 0 to 11, the largest interval class being 6.

In atonal or musical set theory, there are numerous types of intervals, the first being the ordered pitch interval, the distance between two pitches upward or downward. For instance, the interval from C upward to G is 7, and the interval from G downward to C is −7. One can also measure the distance between two pitches without taking into account direction with the unordered pitch interval, somewhat similar to the interval of tonal theory.

The interval between pitch classes may be measured with ordered and unordered pitch-class intervals. The ordered one, also called directed interval, may be considered the measure upwards, which, since we are dealing with pitch classes, depends on whichever pitch is chosen as 0. For unordered pitch-class intervals, see interval class.[28]

Generic and specific intervals

In diatonic set theory, specific and generic intervals are distinguished. Specific intervals are the interval class or number of semitones between scale steps or collection members, and generic intervals are the number of diatonic scale steps (or staff positions) between notes of a collection or scale.

Notice that staff positions, when used to determine the conventional interval number (second, third, fourth, etc.), are counted including the position of the lower note of the interval, while generic interval numbers are counted excluding that position. Thus, generic interval numbers are smaller by 1, with respect to the conventional interval numbers.

Comparison

Specific interval Generic interval Diatonic name
Number of semitones Interval class
0 0 0 Perfect unison
1 1 1 Minor second
2 2 1 Major second
3 3 2 Minor third
4 4 2 Major third
5 5 3 Perfect fourth
6 6 3
4 		Augmented fourth
Diminished fifth
7 5 4 Perfect fifth
8 4 5 Minor sixth
9 3 5 Major sixth
10 2 6 Minor seventh
11 1 6 Major seventh
12 0 7 Perfect octave

Generalizations and non-pitch uses

Division of the measure/chromatic scale, followed by pitch/time-point series.  Play 

The term "interval" can also be generalized to other music elements besides pitch. David Lewin's Generalized Musical Intervals and Transformations uses interval as a generic measure of distance between time points, timbres, or more abstract musical phenomena.[29][30]

See also

Notes

  1. ↑ Prout, Ebenezer (1903), "I-Introduction", Harmony, Its Theory And Practise (30th edition, revised and largely rewritten ed.), London: Augener; Boston: Boston Music Co., p. 1, ISBN 978-0781207836
  2. 1 2 Lindley, Mark/Campbell, Murray/Greated, Clive. "Interval". In Macy, Laura. Grove Music Online. Oxford Music Online. Oxford University Press. (subscription required)
  3. ↑ Aldwell, E; Schachter, C.; Cadwallader, A., "Part 1: The Primary Materials and Procedures, Unit 1", Harmony and Voice Leading (4th ed.), Schirmer, p. 8, ISBN 978-0495189756
  4. ↑ Duffin, Ross W. (2007), "3. Non-keyboard tuning", How Equal Temperament Ruined Harmony (and Why You Should Care) (1st ed.), W. W. Norton, ISBN 978-0-393-33420-3
  5. 1 2 3 "Prime (ii). See Unison" (from Prime. Grove Music Online. Oxford University Press. Accessed August 2013. (subscription required))
  6. 1 2 3 The term Tritone is sometimes used more strictly as a synonym of augmented fourth (A4).
  7. 1 2 The perfect and the augmented unison are also known as perfect and augmented prime.
  8. ↑ The minor second (m2) is sometimes called diatonic semitone, while the augmented unison (A1) is sometimes called chromatic semitone.
  9. 1 2 3 4 5 6 7 The expression diatonic scale is herein strictly defined as a 7-tone scale which is either a sequence of successive natural notes (such as the C-major scale, C–D–E–F–G–A–B, or the A-minor scale, A–B–C–D–E–F–G) or any transposition thereof. In other words, a scale that can be written using seven consecutive notes without accidentals on a staff with a conventional key signature, or with no signature. This includes, for instance, the major and the natural minor scales, but does not include some other seven-tone scales, such as the melodic minor and the harmonic minor scales (see also Diatonic and chromatic).
  10. 1 2 Definition of Perfect consonance in Godfrey Weber's General music teacher, by Godfrey Weber, 1841.
  11. ↑ Kostka, Stephen; Payne, Dorothy (2008). Tonal Harmony, p. 21. First Edition, 1984.
  12. ↑ Prout, Ebenezer (1903). Harmony: Its Theory and Practice, 16th edition. London: Augener & Co. (facsimile reprint, St. Clair Shores, Mich.: Scholarly Press, 1970), p. 10. ISBN 0-403-00326-1.
  13. ↑ See for example William Lovelock, The Rudiments of Music (New York: St Martin's Press; London: G. Bell, 1957): , reprinted 1966, 1970, and 1976 by G. Bell, 1971 by St Martins Press, 1981, 1984, and 1986 London: Bell & Hyman. ISBN 9780713507447 (pbk).
  14. ↑ Drabkin, William (2001). "Fourth". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
  15. ↑ Helmholtz, Hermann L. F. On the Sensations of Tone as a Theoretical Basis for the Theory of Music Second English Edition translated by Ellis, Alexander J. (1885) reprinted by Dover Publications with new introduction (1954) ISBN 0-486-60753-4, page 182d "Just as the coincidences of the two first upper partial tones led us to the natural consonances of the Octave and Fifth, the coincidences of higher upper partials would lead us to a further series of natural consonances."
  16. 1 2 3 Cope, David (1997). Techniques of the Contemporary Composer, pp. 40–41. New York, New York: Schirmer Books. ISBN 0-02-864737-8.
  17. 1 2 Wyatt, Keith (1998). Harmony & Theory... Hal Leonard Corporation. p. 77. ISBN 0-7935-7991-0.
  18. 1 2 Bonds, Mark Evan (2006). A History of Music in Western Culture, p.123. 2nd ed. ISBN 0-13-193104-0.
  19. ↑ Aikin, Jim (2004). A Player's Guide to Chords and Harmony: Music Theory for Real-World Musicians, p. 24. ISBN 0-87930-798-6.
  20. ↑ Károlyi, Otto (1965), Introducing Music, p. 63. Hammondsworth (England), and New York: Penguin Books. ISBN 0-14-020659-0.
  21. 1 2 General rule 1 achieves consistency in the interpretation of symbols such as CM7, Cm6, and C+7. Some musicians legitimately prefer to think that, in CM7, M refers to the seventh, rather than to the third. This alternative approach is legitimate, as both the third and seventh are major, yet it is inconsistent, as a similar interpretation is impossible for Cm6 and C+7 (in Cm6, m cannot possibly refer to the sixth, which is major by definition, and in C+7, + cannot refer to the seventh, which is minor). Both approaches reveal only one of the intervals (M3 or M7), and require other rules to complete the task. Whatever is the decoding method, the result is the same (e.g., CM7 is always conventionally decoded as C–E–G–B, implying M3, P5, M7). The advantage of rule 1 is that it has no exceptions, which makes it the simplest possible approach to decode chord quality.
    According to the two approaches, some may format CM7 as CM7 (general rule 1: M refers to M3), and others as CM7 (alternative approach: M refers to M7). Fortunately, even CM7 becomes compatible with rule 1 if it is considered an abbreviation of CMM7, in which the first M is omitted. The omitted M is the quality of the third, and is deduced according to rule 2 (see above), consistently with the interpretation of the plain symbol C, which by the same rule stands for CM.
  22. ↑ All triads are tertian chords (chords defined by sequences of thirds), and a major third would produce in this case a non-tertian chord. Namely, the diminished fifth spans 6 semitones from root, thus it may be decomposed into a sequence of two minor thirds, each spanning 3 semitones (m3 + m3), compatible with the definition of tertian chord. If a major third were used (4 semitones), this would entail a sequence containing a major second (M3 + M2 = 4 + 2 semitones = 6 semitones), which would not meet the definition of tertian chord.
  23. ↑ Hindemith, Paul (1934). The Craft of Musical Composition. New York: Associated Music Publishers. Cited in Cope (1997), p. 40-41.
  24. ↑ Perle, George (1990). The Listening Composer, p. 21. California: University of California Press. ISBN 0-520-06991-9.
  25. ↑ Gioseffo Zarlino, Le Istitutione harmoniche ... nelle quali, oltre le materie appartenenti alla musica, si trovano dichiarati molti luoghi di Poeti, d'Historici e di Filosofi, si come nel leggerle si potrà chiaramente vedere (Venice, 1558): 162.
  26. ↑ J. F. Niermeyer, Mediae latinitatis lexicon minus: Lexique latin médiéval–français/anglais: A Medieval Latin–French/English Dictionary, abbreviationes et index fontium composuit C. van de Kieft, adiuvante G. S. M. M. Lake-Schoonebeek (Leiden: E. J. Brill, 1976): 955. ISBN 90-04-04794-8.
  27. ↑ Robert De Handlo: The Rules, and Johannes Hanboys, The Summa: A New Critical Text and Translation, edited and translated by Peter M. Lefferts. Greek & Latin Music Theory 7 (Lincoln: University of Nebraska Press, 1991): 193fn17. ISBN 0803279345.
  28. ↑ Roeder, John. "Interval Class". In Macy, Laura. Grove Music Online. Oxford Music Online. Oxford University Press. (subscription required)
  29. ↑ Lewin, David (1987). Generalized Musical Intervals and Transformations, for example sections 3.3.1 and 5.4.2. New Haven: Yale University Press. Reprinted Oxford University Press, 2007. ISBN 978-0-19-531713-8
  30. ↑ Ockelford, Adam (2005). Repetition in Music: Theoretical and Metatheoretical Perspectives, p. 7. ISBN 0-7546-3573-2. "Lewin posits the notion of musical 'spaces' made up of elements between which we can intuit 'intervals'....Lewin gives a number of examples of musical spaces, including the diatonic gamut of pitches arranged in scalar order; the 12 pitch classes under equal temperament; a succession of time-points pulsing at regular temporal distances one time unit apart; and a family of durations, each measuring a temporal span in time units....transformations of timbre are proposed that derive from changes in the spectrum of partials..."

Gardner, Carl E. (1912) - Essentials of Music Theory, p. 38, http://ia600309.us.archive.org/23/items/essentialsofmusi00gard/essentialsofmusi00gard.pdf

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