Augmented octave

In modern Western tonal music theory an augmented octave is the sum of a perfect octave and an augmented unison or chromatic semitone. It is the interval between two notes, with the same note letter on staff positions an octave apart, whose alterations cause them, in ordinary equal temperament, to be thirteen semitones apart. In other words, it is a perfect octave which has been widened by a half-step, such as B and B or C and C; it is a compound augmented unison. It is the enharmonic equivalent of a minor ninth.[1]

Augmented octave
Inversesee "Augmented unison"
Other namesAugmented eighth
Interval class1
Just interval25:12
Equal temperament1300
Just intonation1271
Augmented octave on C. About this soundPlay 

See alsoEdit


  1. ^ William Drabkin, "Octave (i)", in Grove Music Online. Oxford Music Online. Accessed February 2012. (subscription needed)