Flat (music)
In music, flat means lower in pitch. It may either be used generically, meaning any lowering of pitch, or refer to a particular size: lowering pitch by a chromatic semitone. A flat is the opposite of a sharp (♯) which raises pitch by the same amount that a flat lowers it.
♭
U+266D ♭ MUSIC FLAT SIGN (♭)
U+0062 b LATIN SMALL LETTER B
U+1D12B 
MUSICAL SYMBOL DOUBLE FLAT
U+266F ♯ MUSIC SHARP SIGN
The flat symbol (♭) is used in two ways: It is placed in key signatures to mark lines whose notes are flattened throughout that section of music; it may also be an "accidental" that precedes an individual note and indicates that the note should be lowered temporarily, until the following bar line.
Pitch change[edit]
The flat symbol is ♭ is a stylised lowercase ‘b’ , derived from Italian be molle for "soft B" and German blatt for "planar, dull". It indicates that the note to which it is applied is played one semitone lower, or in modern tuning exactly 100 cents.[1][2]
In traditional and modern microtonal temperaments the size of sharps or flats (chromatic semitones) is normally smaller than the size of the diatonic semitones found between E and F or B and C. In those tuning systems, the size of the shift made by the ♭ symbol usually conforms to the smaller-sized lowering of pitch;[a] however, for some tuning systems it may instead be replaced by a different symbol for raising and lowering pitch, depending on the author's preference and the intricacy of any microtuning involved.[b]
The Unicode character ♭ (U+266D) can be found in the block Miscellaneous Symbols; its HTML entity is ♭ . Other assigned flat signs are as follows:
In environments where the symbol is not supported, or in specific text notation, a double flat is sometimes written as ♭♭, bb, etc. Likewise, a triple flat can also be written as ♭♭♭, etc.
