augmented fourth noun1 •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. formsaugmented fourths
