A1 — 55.00 Hz
A1 (MIDI 33) vibrates 55.00 times per second at standard concert pitch. Play the reference tone below, or tune to it with the online tuner.
A1 at different reference pitches
| Reference (A4) | A1 frequency | Used for |
|---|---|---|
| 415 Hz | 51.88 Hz | Baroque pitch |
| 432 Hz | 54.00 Hz | “Verdi” pitch |
| 440 Hz | 55.00 Hz | Standard concert pitch |
| 442 Hz | 55.25 Hz | European orchestras |
| 444 Hz | 55.50 Hz | European orchestras |
Physical properties
- Period: one cycle every 18.18 ms
- Wavelength in air: ≈ 6.24 m (at 20 °C, 343 m/s)
- MIDI note number: 33
- Octave up: A2 = 110.00 Hz · Octave down: 27.50 Hz