C♯9 / D♭9
8,869.844Hz at concert pitch
Press to hear a pure sine tone at this pitch.
MIDI note
121
Piano key
—
Octave
9
Frequency
8,869.844 Hz
Period
0.1127 ms
Wavelength
0.0387 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 C♯s share one. Enharmonic spellings (C♯9 and D♭9) name the same pitch two ways. This note falls outside the 88-key piano, so it has no piano key number.
At other reference pitches
| Reference (A4) | C♯9 frequency | Where you meet it |
|---|---|---|
| 432 Hz | 8,708.574 Hz | the alternative-tuning circle |
| 440 Hzstandard | 8,869.844 Hz | the ISO 16 standard — concert pitch |
| 442 Hz | 8,910.162 Hz | many European orchestras tune a touch sharp |
| 443 Hz | 8,930.32 Hz | some sharper continental orchestras |
Every row is C♯9 — only the A4 you tune to changes. A frequency scales straight with the reference: C♯9 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.