Audio Pitch Changer (Key Changer)

Move a song into a key that suits your voice or instrument, tune a recording to match a band, or make a backing track a little higher or lower. Choose how many semitones to move and, if needed, fine-tune in cents. By default the tempo stays the same; you can also change pitch and speed together, the way a record sounds at the wrong speed. Files are processed in your browser and never uploaded.

How to use this tool

1. Choose one or more audio files.
2. Enter the change in semitones (+2 = a whole step up) and, optionally, cents.
3. Keep "Keep the tempo" for a key change, or choose "Change speed with the pitch".
4. Optionally type the song's key to see the new one, pick the format and press Calculate.

Formula

Pitch factor = 2^((semitones + cents ÷ 100) ÷ 12) · cents = 1200 × log2(new ÷ old)

Every frequency is multiplied by the factor: +12 semitones doubles them (one octave), −12 halves them. With "Keep the tempo" the audio is resampled by the factor and then time-stretched back to its original length by the ffmpeg engine's atempo filter (WSOLA), a one-time download of about 30 MB; the factor is exact to within 0.04 cent. The stretch can soften the last few hundredths of a second (up to about 30 ms) of a file that stops abruptly. "Change speed with the pitch" uses band-limited resampling in your browser, so the length changes by the same factor and no download is needed.

Example

A song in C major moved up +2 semitones is in D major: every note is 2^(2 ÷ 12) ≈ 1.1225 times higher, so its A at 440 Hz becomes about 493.9 Hz (B). With the tempo kept, a 3:30 song is still 3:30 long; changed like a record, it would last 210 ÷ 1.1225 ≈ 187 s (3:07).