Flat (music)

In music theory, a flat (♭) is an accidental that lowers the pitch of a note by a half step (semitone). It is represented by a symbol resembling a lowercase "b."

The flat symbol is placed to the left of the note it modifies, either in written notation or in chord symbols. For example, B♭ indicates that the note B should be played a half step lower than its natural pitch.

A double flat (♭♭) lowers the pitch of a note by two half steps, or a whole tone.

The use of flats is crucial in establishing key signatures. Keys containing flat key signatures systematically lower specific notes throughout a piece of music. For example, the key of B♭ major has two flats in its key signature: B♭ and E♭. This means that all B's and E's are automatically played a half step lower unless otherwise indicated by a natural sign.

Accidentals, including flats, can also be used outside the key signature to alter a note within a specific measure. These accidentals only apply to the note they precede within that measure and octave.

Flats are essential for accurate performance and understanding of music written in keys that require lowered pitches. They are also used to create altered chords and melodic variations.