augmented fourth

augmented fourth (plural augmented fourths)

1. (music) A type of tritone in musical composition. It spans four diatonic scale degrees like a perfect fourth but with an extension of a chromatic semitone. The number of diatonic degrees it spans is what distinguishes it from a diminished fifth.

   e.g. C - F is a perfect fourth, C - F# is an augmented fourth, and C - F♭ is a diminished fourth.

   An augmented fourth on C:
   

   

Aurally and while using well temperament or 12-tone equal temperament, it is impossible to distinguish between an augmented fourth and a diminished fifth. For this reason one would call it a "tritone" in a context such as ear training, but distinguish between an augmented fourth and a diminished fifth when, for example, analysing a score.

In most other tunings, however, the augmented fourth and diminished fifth are of different sizes.

• augmented fifth
• diminished fourth
• perfect fourth

• dissonance
• musical interval
• tritone