Transpose by semitones without touching tempo, stretch tempo without touching pitch, or tie them together like a turntable. Everything is computed on this machine.
Nothing is uploaded. The file is decoded, analysed and rendered inside your browser, and never leaves this machine.
Pitch & Tempo changes the key of a track without altering its speed, and its speed without altering its key. Singers drop a song one or two semitones to reach the top notes, and players slow a solo to 70 % to learn it without hearing a chipmunk.
The whole engine runs in your browser: the file is decoded with Web Audio, analysed for key and tempo, and time-stretched with the formant-preserving Signalsmith Stretch engine compiled to WebAssembly. No upload, no queue, no account.
Key, tempo and the ink waveform appear within seconds, measured locally.
Semitones, cents and tempo percentage each have their own control, with the resulting key and BPM printed live.
Drag an A–B loop to practise a passage, then download a WAV that lines up in your DAW.