Flat (music)

In music, flat means lower in pitch. It may either be used in a general sense to mean any lowering of pitch, or to specifically refer to lowering pitch by a semitone. A flat is the opposite of a sharp (♯) which indicates a raised pitch in the same way.

The flat symbol (♭) appears in key signatures to indicate which notes are flat throughout a section of music, and also in front of individual notes as an accidental, indicating that the note is flat until the next bar line.

The symbol ♭ 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. In the standard modern tuning system, 12 tone equal temperament, this corresponds to 100 cents.

In older tuning systems (from the 16th and 17th century), and in modern microtonal tunings, the difference in pitch indicated by a sharp or flat is normally smaller than the standard semitone. For example, in the old quarter-comma meantone system a flat lowers a note's pitch by 76.05 cents,, and in just intonation a flat commonly lowers a note's pitch by 70.57 cents. In Pythagorean tuning a flat lowers the pitch by 113.7 cents, and in well temperaments, a flat may be different sizes. Intricate systems of microtuning may replace the standard flat or sharp with different symbols for raising and lowering pitch. In 53 equal temperament tuning sharps and flats have two or three different sub-levels, and notation for flattening notes varies, but usually involves several different symbols; one of the sets of 53 TET flat symbols is ♭ (67.9 cents), (45.3 cents), and ↓ (22.6 cents), used both separately and in combinations.

A double flat (𝄫) lowers a note by two semitones (a whole step).

A quarter-tone flat, half flat or demiflat indicates the use of quarter tones; it may be marked with various symbols including a flat with a slash (), a flat with a 4 (

𝄳), or areversed flat sign (). A three-quarter-tone flat, flat and a half or sesquiflat is represented by a demiflat and a whole flat (). The symbols -, ↓, , among others, represent comma flat or eighth-tone flat.

A triple flat (♭𝄫 or 𝄫♭) is very rare. As expected, it lowers a note by three semitones (a whole tone and semitone). (For example, B♭𝄫 is enharmonic with A♭.)

While this system allows for higher multiples of flats, there are only a few examples of triple flats in the literature. However, quadruple flats or beyond may be required in some non-standard tuning systems such as 53 equal temperament. A quadruple flat would be indicated by the symbol 𝄫𝄫.

	Order of flats in key signatures
	The last two rows are shaded, indicating keys that are generally avoided, in part because they use inconvenient enharmonic notes, denoted with "*". In the standard tuning system of 12 equal temperament, the key of C♭ major, with 7 flats is enharmonically equivalent with B major, which only requires 5 sharps.

The order of flats in key signatures is

B♭, E♭, A♭, D♭, G♭, C♭, F♭

The corresponding order of keys also follows the circle of fifths sequence:

F, B♭, E♭, A♭, D♭, G♭, C♭

Starting with no flats or sharps (C major), adding the first flat (B♭) indicates F major; adding the next (E♭) indicates B♭ major, and so on, backwards through the circle of fifths.

Some keys (such as C♭ major with seven flats) may be written as an enharmonically equivalent key (B major with five sharps in this case). In rare cases the flat keys may be extended further:

F♭ → B𝄫 → E𝄫 → A𝄫 → D𝄫 → G𝄫 → C𝄫

requiring double flats in the key signature. These are generally avoided as impractical, and the simpler, equivalent key signature is used instead. This principle applies similarly to the sharp keys.

The staff below shows a key signature with three flats (E♭ major or its relative minor C minor), followed by a note with a flat preceding it: The flat symbol placed on the note indicates that it is a D♭.

In standard 12 tone equal temperament tuning, lowering a note's pitch by a semitone results in a note that is enharmonically equivalent to the adjacent named note. In this system, B♭ and A♯ are considered to be equivalent. In other, non-standard tuning systems, however, this is not the case.

Accidentals are placed to the left of the note head.

They apply to the note on which they are placed and to subsequent similar notes in the same measure and octave. In modern notation they do not apply to notes in other octaves, but this was not always the convention. To cancel an accidental later in the same measure and octave, another accidental such as a natural (♮) or a sharp (♯) may be used.

• Historically, raising a double flat to a single flat would be notated using a natural and flat sign (♮♭) or vice-versa (♭♮) instead of using only a flat sign (♭). In modern notation the leading natural sign is often omitted. The combination ♮♭ can be also written when changing a sharp to flat.

  

• In environments where the 𝄫 symbol is not supported, or in specific text notation, a double flat can be written with ♭♭, two lower-case b's (bb), etc. Likewise, a triple flat can also be written as ♭♭♭, etc.
• In environments where the or 𝄳 symbol is not supported, or in specific text notation, a half flat can be written as a lower-case d. Likewise, a flat and a half can also be written as d♭ or db.
• To allow extended just intonation, composer Ben Johnston uses a flat as an accidental to indicate a note is lowered 70.6 cents.

The Unicode character ♭ (U+266D) can be found in the block Miscellaneous Symbols; its HTML entity is ♭. Other assigned flat signs can be found in the Musical Symbols block and are as follows:

• U+1D12B 𝄫 MUSICAL SYMBOL DOUBLE FLAT
• U+1D12C 𝄬 MUSICAL SYMBOL FLAT UP
• U+1D12D 𝄭 MUSICAL SYMBOL FLAT DOWN
• U+1D133 𝄳 MUSICAL SYMBOL QUARTER TONE FLAT

• Electronic tuner – Device used to tune musical instruments

• Media related to Flats (music) at Wikimedia Commons