C#1 — 34.65 Hz
C#1 (MIDI 25) vibrates 34.65 times per second at standard concert pitch. Play the reference tone below, or tune to it with the online tuner.
C#1 at different reference pitches
| Reference (A4) | C#1 frequency | Used for |
|---|---|---|
| 415 Hz | 32.68 Hz | Baroque pitch |
| 432 Hz | 34.02 Hz | “Verdi” pitch |
| 440 Hz | 34.65 Hz | Standard concert pitch |
| 442 Hz | 34.81 Hz | European orchestras |
| 444 Hz | 34.96 Hz | European orchestras |
Physical properties
- Period: one cycle every 28.86 ms
- Wavelength in air: ≈ 9.90 m (at 20 °C, 343 m/s)
- MIDI note number: 25
- Octave up: C#2 = 69.30 Hz · Octave down: 17.32 Hz