Diminished octave

diminished octave

Inverse	Augmented unison
Name
Other names	Diminished eighth
Abbreviation	d8[1]
Size
Semitones	11
Interval class	1
Just interval	48:25
Cents
Equal temperament	1100
24 equal temperament	1100
Just intonation	1129

Diminished octave on C  Play .

Diminished octave on C-sharp  Play .

In classical music from Western culture, a diminished octave ( Play ) is an interval produced by narrowing a perfect octave by a chromatic semitone.^[1] As such, the two notes are denoted by the same letter but have different accidentals. For instance, the interval from C4 to C5 is a perfect octave, twelve semitones wide, and both the intervals from C♯4 to C5, and from C4 to C♭5 are diminished octaves, spanning eleven semitones. Being diminished, it is considered a dissonant interval.^[2]

The diminished octave is enharmonically equivalent to the major seventh.

Sources

1. Benward & Saker (2003). Music: In Theory and Practice, Vol. I, p.54. ISBN 978-0-07-294262-0. Specific example of an d8 not given but general example of perfect intervals described.
2. Benward & Saker (2003), p.92.