A1
Reviewed for accuracy · Maintained by Justin Evans
A1 highlighted — use the view toggle to see all 88 keys.
Piano key
13 of 88
Octave
1
Frequency
55 Hz
MIDI number
33
Key color
White key
Pitch class
A · G## · Bbb
What is A1?
A1 is the A in octave 1 — the 13th key of the 88 on a full-size piano, counted from the bottom. In standard tuning it sounds at 55 Hz. It sits 27 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 110 Hz and the one below at 27.5 Hz. The same piano key can be written as A, G##, Bbb depending on the musical context — same sound, different spelling.
Nearby notes
Every A on the keyboard: