A♯0 / B♭0
Reviewed for accuracy · Maintained by Justin Evans
A♯0 highlighted — use the view toggle to see all 88 keys.
Piano key
2 of 88
Octave
0
Frequency
29.14 Hz
MIDI number
22
Key color
Black key
Pitch class
A# · Bb · Cbb
What is A♯0?
A♯0 is the A♯ in octave 0 — the 2nd key of the 88 on a full-size piano, counted from the bottom. In standard tuning it sounds at 29.14 Hz. It sits 38 half-steps below middle C (C4).
To find it, locate any group of two black keys: the white key just to their left is a C. Count down from middle C (C4) 4 octaves to reach octave 0, then step to A♯.
Every octave doubles the frequency: the A♯ one octave up sounds at 58.28 Hz and the one below at 14.57 Hz. The same piano key can be written as A#, Bb, Cbb depending on the musical context — same sound, different spelling.
Nearby notes
Every A♯ on the keyboard: