Chromatic semitone

Chromatic semitone

Augmented unison
Inverse Diminished octave
Name
Other names Chromatic semitone
Abbreviation A1
Size
Semitones 1
Interval class 1
Just interval 25:24
Cents
Equal temperament 100
24 equal temperament 100
Just intonation 71


In modern Western tonal music theory an augmented unison or augmented prime[3] is the interval between two notes on the same staff position, or denoted by the same note letter, whose alterations cause them, in ordinary equal temperament, to be one semitone apart. In other words, it is a unison where one note has been altered by a half-step, such as B and B or C and C. The interval is often described as a chromatic semitone.[4] In 12 tone equal temperament, it is the enharmonic equivalent of a diatonic semitone or minor second,[1] although in other tunings the diatonic semitone is a wider interval.

Diminished unison

The augmented unison is occasionally referred to also as a diminished unison. The first author to employ this term was apparently William White, in 1907.[5] Many sources reject the possibility or utility of the diminished unison on the grounds that any alteration to the unison increases its size, thus augmenting rather than diminishing it.[6][7][8][9][10][11][12][13]

See also

References