Diminished octave

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diminished octave
Inverse
Augmented unison
Name
Other namesDiminished eighth
Abbreviationd8[1]
Size
Semitones11
Interval class1
Just interval48:25, 256:135,[2] 4096:2187
Cents
12-Tone equal temperament1100[2]
Just intonation1129, 1108,[2] 1086
Diminished octave on C Play.
Diminished octave on C-sharp Play.

In music from

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 C4 to C5 and from C4 to C5 are diminished octaves, spanning eleven semitones. Being diminished, it is considered a dissonant interval.[3]

The diminished octave is enharmonically equivalent to the major seventh.

References