A2
110Hz at concert pitch
Press to hear a pure sine tone at this pitch.
MIDI note
45
Piano key
25
Octave
2
Frequency
110 Hz
Period
9.0909 ms
Wavelength
3.1182 m
Pitch class
A
Notation
SPN
MIDI is the note number synths and software pass around (0–127). Pitch class is the note without its octave — all the As share one.
At other reference pitches
| Reference (A4) | A2 frequency | Where you meet it |
|---|---|---|
| 432 Hz | 108 Hz | the alternative-tuning circle |
| 440 Hzstandard | 110 Hz | the ISO 16 standard — concert pitch |
| 442 Hz | 110.5 Hz | many European orchestras tune a touch sharp |
| 443 Hz | 110.75 Hz | some sharper continental orchestras |
Every row is A2 — only the A4 you tune to changes. A frequency scales straight with the reference: A2 at 432 Hz is the 440 Hz value times 432⁄440.
Move around
Every A
Chords with A in them
A appears in each of these — see the whole chord grid.