C♯1 / D♭1
34.648Hz at concert pitch
Press to hear a pure sine tone at this pitch.
MIDI note
25
Piano key
5
Octave
1
Frequency
34.648 Hz
Period
28.8617 ms
Wavelength
9.8996 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♯1 and D♭1) name the same pitch two ways.
At other reference pitches
| Reference (A4) | C♯1 frequency | Where you meet it |
|---|---|---|
| 432 Hz | 34.018 Hz | the alternative-tuning circle |
| 440 Hzstandard | 34.648 Hz | the ISO 16 standard — concert pitch |
| 442 Hz | 34.805 Hz | many European orchestras tune a touch sharp |
| 443 Hz | 34.884 Hz | some sharper continental orchestras |
Every row is C♯1 — only the A4 you tune to changes. A frequency scales straight with the reference: C♯1 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.