A♯1 / B♭1
Reviewed for accuracy · Maintained by Justin Evans
A♯1 highlighted — use the view toggle to see all 88 keys.
Piano key
14 of 88
Octave
1
Frequency
58.27 Hz
MIDI number
34
Key color
Black key
Pitch class
A# · Bb · Cbb
What is A♯1?
A♯1 is the A♯ in octave 1 — the 14th key of the 88 on a full-size piano, counted from the bottom. In standard tuning it sounds at 58.27 Hz. It sits 26 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) 3 octaves to reach octave 1, then step to A♯.
Every octave doubles the frequency: the A♯ one octave up sounds at 116.54 Hz and the one below at 29.14 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: