Notation & Symbols
Double Flat
A double flat is a sign of two flats side by side that lowers a note by two half steps, a whole step. B double-flat is played on the same key as A; the sign appears mostly in flat keys and diminished chords.
A double flat lowers a note by two half steps, a whole step. Its sign is two flat signs side by side, written before the note like any other accidental. B double-flat is played on the key we usually call A, and E double-flat on D.
Why not just write A?
For the same reason as the double sharp: letter names show what a note is doing. Chords built in thirds use alternate letters, so their spelling keeps that structure visible in any key. The diminished seventh chord on C is built on the letters C, E, G and B, each lowered as the chord requires: C, E♭, G♭ and B double-flat. Spelled with an A instead, it would no longer look like a stack of thirds, and the interval from C up to B double-flat, a diminished seventh, would be hidden.
You will meet double flats mainly in keys with many flats, where an already flat note is lowered again, and in diminished and other chromatic chords.
Canceling a double flat
A natural cancels it completely. To go from B double-flat back to B-flat in the same bar, modern editions simply write a flat; some older editions write a natural followed by a flat.
Reading tip
Read it in two steps: find the plain letter, then move two keys to the left. B, then B♭ one key down, then B double-flat two keys down, on A. The enharmonic equivalent name tells you which key to press; the written name tells you what the note is doing.
Practice with Double sharps and double flats and see the chord in The diminished 7th.
Common questions
What does a double flat look like?
Two flat signs side by side, placed just before the note.
Is B double-flat the same as A?
On the piano, yes: both are played on the same key (enharmonic equivalent notes). The name B double-flat is used when the note's role in the key or chord calls for a kind of B.
Practice it: free worksheets
Double sharps and double flatsA sharp raises a note one half step; a flat lowers it one (Handouts 06–08). Now and then a note has to move two. The double sharp raises it two half steps, the double flat lowers it two. The key you play is one you already know — only its name is new.
The diminished 7thTake a diminished triad and stack one more minor third on top. Now every gap in the chord is the same size — and that one fact gives it every strange property it has. Written B°7 or Bdim7.
Accidentals on the staffA sharp (♯) raises a note, a flat (♭) lowers it, and a natural (♮) cancels either one. Name every note with its accidental — write F♯, not just F. (Need a refresher? See Handouts 06, 07 and 08.)