C1
32.703Hz at concert pitch
Press to hear a pure sine tone at this pitch.
MIDI note
24
Piano key
4
Octave
1
Frequency
32.703 Hz
Period
30.5782 ms
Wavelength
10.4883 m
Pitch class
C
Notation
SPN
MIDI is the note number synths and software pass around (0–127). Pitch class is the note without its octave — all the Cs share one.
The octave-numbering trap: this site uses scientific pitch notation, where MIDI 24 is C1. Yamaha gear labels the same key C0 and some trackers call it C2. The MIDI number never moves — only the octave name printed on the box does.
At other reference pitches
| Reference (A4) | C1 frequency | Where you meet it |
|---|---|---|
| 432 Hz | 32.109 Hz | the alternative-tuning circle |
| 440 Hzstandard | 32.703 Hz | the ISO 16 standard — concert pitch |
| 442 Hz | 32.852 Hz | many European orchestras tune a touch sharp |
| 443 Hz | 32.926 Hz | some sharper continental orchestras |
Every row is C1 — only the A4 you tune to changes. A frequency scales straight with the reference: C1 at 432 Hz is the 440 Hz value times 432⁄440.
Move around
Every C
Chords with C in them
C appears in each of these — see the whole chord grid.