A♯3 / B♭3
Reviewed for accuracy · Maintained by Justin Evans
A♯3 highlighted — use the view toggle to see all 88 keys.
Piano key
38 of 88
Octave
3
Frequency
233.08 Hz
MIDI number
58
Key color
Black key
Pitch class
A# · Bb · Cbb
What is A♯3?
A♯3 is the A♯ in octave 3 — the 38th key of the 88 on a full-size piano, counted from the bottom. In standard tuning it sounds at 233.08 Hz. It sits 2 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) 1 octave to reach octave 3, then step to A♯.
Every octave doubles the frequency: the A♯ one octave up sounds at 466.16 Hz and the one below at 116.54 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: