C9
8,372.018Hz at concert pitch
Press to hear a pure sine tone at this pitch.
MIDI note
120
Piano key
—
Octave
9
Frequency
8,372.018 Hz
Period
0.1194 ms
Wavelength
0.041 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. This note falls outside the 88-key piano, so it has no piano key number.
The octave-numbering trap: this site uses scientific pitch notation, where MIDI 120 is C9. Yamaha gear labels the same key C8 and some trackers call it C10. The MIDI number never moves — only the octave name printed on the box does.
At other reference pitches
| Reference (A4) | C9 frequency | Where you meet it |
|---|---|---|
| 432 Hz | 8,219.8 Hz | the alternative-tuning circle |
| 440 Hzstandard | 8,372.018 Hz | the ISO 16 standard — concert pitch |
| 442 Hz | 8,410.073 Hz | many European orchestras tune a touch sharp |
| 443 Hz | 8,429.1 Hz | some sharper continental orchestras |
Every row is C9 — only the A4 you tune to changes. A frequency scales straight with the reference: C9 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.