Audio Speed & Pitch
Change tempo and key independently — slow a track without chipmunk voices.
Change Tempo and Key Independently
Playing a file faster raises its pitch, and playing it slower drops it. That coupling is why a slowed-down song sounds like it is underwater and a sped-up voice sounds like a cartoon. For transcription, language practice or music work you usually want one without the other.
This tool separates them properly. Speed is changed by stretching the waveform in time using overlap-add with a similarity search, which keeps the pitch exactly where it was. Pitch is changed by resampling and then stretching back, which moves the key while holding the duration. The two controls are genuinely independent — you can slow a track to 75% and still transpose it up a fifth.
Key features
- Speed from 0.5× to 2× — with the key held constant, so a slowed track still sounds like the original performance.
- Pitch across two octaves — twelve semitones up or down, with the duration untouched.
- Both at once — the controls stack, so you can change tempo and key in the same render.
- Presets for the common cases — slowed, nightcore and deep-voice settings are one click away.
- Phase-coherent stretching — each grain is aligned to what came before it, which is what stops time-stretched audio from warbling.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: Audio Speed & Pitch
- Add your audio
The file is decoded locally and its original length is shown for reference. - Set speed and pitch
Drag the two sliders, or pick a preset. The estimated new length updates as you move the speed control. - Render and listen
Press Render to process the audio, then Play to hear the result before you commit to it. - Download the WAV
Export the processed audio at its new tempo and key.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Audio |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
Why does time-stretched audio sometimes sound odd?
Time stretching works by repeating or dropping short grains of sound and crossfading between them. At extreme settings, or on material with sharp transients like drums, the joins become audible. Moderate changes — roughly 0.75× to 1.5× — are usually transparent.
Can I slow music down to learn a part?
Yes, and that is one of the main reasons this tool keeps pitch constant. A guitar part slowed to 70% is still in the same key, so what you practise matches what you will play at full speed.
How is this different from just changing playback rate?
Changing playback rate moves speed and pitch together, exactly as a record player does. This stretches the waveform in time instead, so the two can be controlled separately.
Does it work on speech?
Very well. Speech has fewer sharp transients than percussive music, so it survives large stretches cleanly. Slowing a fast talker to 0.7× for transcription is a common use and sounds natural.
Why does rendering take a moment?
Time stretching is real signal processing — every grain is compared against the output so far to find the best alignment. On a few minutes of audio that is a second or two of work, done on your own machine rather than a server.