C2
65.406Hz at concert pitch
Press to hear a pure sine tone at this pitch.
MIDI note
36
Piano key
16
Octave
2
Frequency
65.406 Hz
Period
15.2891 ms
Wavelength
5.2442 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 36 is C2. Yamaha gear labels the same key C1 and some trackers call it C3. The MIDI number never moves — only the octave name printed on the box does.
At other reference pitches
| Reference (A4) | C2 frequency | Where you meet it |
|---|---|---|
| 432 Hz | 64.217 Hz | the alternative-tuning circle |
| 440 Hzstandard | 65.406 Hz | the ISO 16 standard — concert pitch |
| 442 Hz | 65.704 Hz | many European orchestras tune a touch sharp |
| 443 Hz | 65.852 Hz | some sharper continental orchestras |
Every row is C2 — only the A4 you tune to changes. A frequency scales straight with the reference: C2 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.