Pitch without tempo · tempo without pitch

Change the key, or the speed

Slow a track down without the pitch dropping. Move it to your key without it slowing down. For learning parts by ear, singing along and sampling — all inside the browser.

Drag & drop the track you want to move

or click to choose

MP3, WAV, M4A, AAC, FLAC, OGG, Opus, AIFF and more — plus the audio of MP4, MOV, WebM and other video

What Bend does

Speed and key, separately

Slowing a track down normally drags the pitch down with it. Bend treats stretching and pitch as two different things, so at 70% the key has not moved — and the reverse works too: same speed, key up a semitone.

Semitones and cents

Semitone steps, the same units a karaoke machine uses, plus a cent-level fine tune. A recording made at A=442 Hz is off by an amount no semitone can express; that is what the cents control is for.

Hold to hear the original

Switch between converted and original from the same point in the track. A large move always sounds different — whether it sounds better is something you have to hear against the source.

Terms and rules of thumb

Semitone / keyA semitone is one twelfth of an octave, the smallest step in ordinary tuning. "Key +2" on a karaoke machine is two semitones — a whole tone. Note that neighbouring letters are not all a tone apart: C to D is two semitones, E to F is one.
CentsOne hundredth of a semitone. A recording at A=442 Hz sits about 8 cents above A=440; A=432 is about 32 cents below. Offsets that small cannot be written in semitones, which is why there is a separate control for them.
Tempo (%)Playback speed with the original at 100%. At 80% the track is 1.25× longer, and a 120 BPM song plays at 96 BPM. For picking a fast line out by ear, somewhere around 70–80% is usually where the notes separate.
Male ↔ female rangeMoving a song between typical male and female ranges is usually 4 to 5 semitones — a major third or a fourth. Start at −5 or +5, then close in a semitone at a time on whether the highest note of the chorus is reachable.
Why slowing it down does not lower the pitchA tape drops in pitch because it stretches the waveform itself. Bend instead breaks the sound into short slices, describes each as a set of frequencies, and lays them back down at the original pitch — a phase vocoder. That is what makes speed and pitch two independent numbers.
Smearing (artefacts)What that model is bad at is anything that starts instantly: drum hits and cymbals. The further you move, the softer the attacks get and the more the cymbals take on a brushed, grainy quality. Voices and guitars survive far larger moves.

Frequently asked questions

Does the sound change as I move the slider?

No. You set the key and the speed, and pressing "Convert" rebuilds the whole track from there. The browser's own playback controls cannot separate pitch from speed, so rather than imply an instant response and then stall, this makes the moment of conversion explicit. A three-minute track takes a few seconds to a few tens of seconds.

How far can I move it?

Up to ±6 semitones of key, plus cents, and 50–150% of tempo. In practice ±3 to 4 semitones and 70–130% is the range that stays clean; beyond that, drums and cymbals start to smear. The full range is offered anyway so you can decide with your own ears where the limit is for your material.

Is this the same as "key +2" on a karaoke machine?

The same idea. One step of karaoke key is one semitone, so setting the semitone slider to the same number moves a backing track to your key.

How do I find the key that suits me?

If the top of the chorus is a strain, go down; if it sits low and you have breath to spare, go up. Between typical male and female ranges the gap is 4 to 5 semitones. Try ±2 first, then move a semitone at a time — the character of the song shifts as you go, so pick the best-sounding point inside the range you can actually sing.

Can I retune an A=442 or A=432 recording to 440?

Yes, with the cents control. A=442 is about +8 cents, so it needs −8; A=432 is about −32 cents, so it needs +32. The audio analyser (Shape) reports a track's tuning offset in cents — put in that figure with the sign flipped.

Is my audio uploaded?

No. Reading, converting and exporting all happen inside your browser, and the audio is never sent anywhere.