Double Flat
Lowers a note by two semitones — a whole tone, not two separate flats
Related
A double flat is a single sign built from two flat signs; it lowers a note by two semitones, a whole tone: B double flat equals A, E double flat equals D.
It appears in flat keys and chromatic harmony. The lowered seventh of G♭ major is F♭, and flattening it again gives F double flat; some augmented-sixth and diminished-seventh spellings also use double flats. The sign keeps degrees legible rather than making the score harder on purpose.
Do not treat it as two flats acting separately. It is one sign, one whole-tone lowering, valid for that pitch for the rest of the bar. Players who watch only the keyboard confuse it with its enharmonic twin, so read the degree before finding the key.
Sources
- 重降号的含义与用法，参 The New Grove Dictionary of Music and Musicians, "Accidental"；本文为原创表述
Used for fact-checking only; all prose is original.