In music, flat or bemolle (Italian: "soft B") means "lower in pitch". More specifically, in musical notation, flat means "lower in pitch by one semitone (half step)". Flat is the opposite of sharp, which is a raising of pitch.
In music notation, the flat symbol, ?, derived from a stylised lowercase "b", lowers a note by a half step (semitone). For instance, the music below has a key signature with three flats (indicating either E? major or C minor) and the note, D?, has a flat accidental.
Under twelve-tone equal temperament, C? for instance is the same as (or enharmonically equivalent to) B?, and G? is equivalent to F?. In any other tuning system, such enharmonic equivalences in general do not exist. To allow extended just intonation, composer Ben Johnston uses a sharp as an accidental to indicate a note is raised 70.6 cents (ratio 25:24), and a flat to indicate a note is lowered 70.6 cents.
In intonation, flat can also mean "slightly lower in pitch" (by some unspecified amount). If two simultaneous notes are slightly out-of-tune, the lower-pitched one (assuming the higher one is properly pitched) is "flat" with respect to the other. Furthermore, the verb flatten means to lower the pitch of a note, typically by a small musical interval.
Flats are used in the key signatures of
The order of flats in the key signatures of music notation, following the circle of fifths, is B?, E?, A?, D?, G?, C? and F? (mnemonics for which include Battle Ends And Down Goes Charles' Father and Before Eating A Doughnut Get Coffee First).
Double flats also exist, which look like (similar to two flats, ??) and lower a note by two semitones, or a whole step. The Unicode character ? (U+1D12B) in the Musical Symbols block represents the double-flat sign.
A quarter-tone flat or half flat, indicating the use of quarter tones, may be marked with various symbols including a flat with a slash () or a reversed flat sign (). A three-quarter-tone flat, flat and a half or sesquiflat, is represented by a half flat and a regular flat ().