C-1
8.176Hz at concert pitch
Press to hear a pure sine tone at this pitch.
MIDI note
0
Piano key
—
Octave
-1
Frequency
8.176 Hz
Period
122.3092 ms
Wavelength
41.9521 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 0 is C-1. Yamaha gear labels the same key C-2 and some trackers call it C0. The MIDI number never moves — only the octave name printed on the box does.
At other reference pitches
| Reference (A4) | C-1 frequency | Where you meet it |
|---|---|---|
| 432 Hz | 8.027 Hz | the alternative-tuning circle |
| 440 Hzstandard | 8.176 Hz | the ISO 16 standard — concert pitch |
| 442 Hz | 8.213 Hz | many European orchestras tune a touch sharp |
| 443 Hz | 8.232 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.
About this note
The very bottom of the MIDI note range — number 0. In scientific pitch notation that's C in octave −1, roughly 8 Hz, an octave below the lowest note most humans can perceive as pitch. It exists so the numbering has somewhere to start.
Move around
Every C
Chords with C in them
C appears in each of these — see the whole chord grid.