Change the pitch of a song without changing its speed, or slow a recording down without lowering it - to sing along in your own range, learn a fast solo, transcribe a lecture or match a track to another. When a song opens, the page estimates its key and BPM, so you can pick the key or tempo you want and let it work out the move. The pitch and speed are changed by Signalsmith Stretch, a high-quality time-stretching library, with an option that keeps voices sounding like themselves when the pitch moves. You hear each change as you make it, and can loop the bar you are practising. It is free to use, with no account and no upload limit, and it runs entirely in your browser: nothing is uploaded, and while the page stays open, a feature you have already used keeps working offline.
- Does changing the pitch change the speed?
- No. Pitch and tempo are separate here: a song moved up two semitones keeps its length, and one slowed to 75% keeps its key. Changing both at once works too.
- What does formant preservation do?
- A voice has a pitch, the notes sung, and formants, the resonances of the throat and mouth that make it sound like that person. Plain pitch shifting moves both, which is why a raised voice sounds like a cartoon. With Keep voices natural on, the notes move and the formants stay, so the singer still sounds like themselves a few semitones up or down. Moves of more than about five semitones start to sound processed, as they do in any pitch shifter.
- How many semitones is a key change?
- One semitone is one step on a piano, black keys included, so moving from C to D is +2 and from G down to E is −3. The page estimates the original key when the song opens (correct it if you know better); choose the key you want under Change to and it moves the pitch for you.
- How does it find the key of a song?
- It measures which of the twelve notes sound most across the first minutes of the song and compares that with the pattern each major and minor key is known for (the Krumhansl-Kessler key profiles). It is an estimate: a song that changes key or borrows chords can mislead it, and a key is most often confused with its relative major or minor - C major and A minor use the same notes - which is why the page offers the next most likely key too.
- How do I find the right key for my voice?
- Play the song and move it down a semitone at a time until the high notes are comfortable, or up until the low notes are; the page shows the key you end up in. A song recorded by a singer with a much higher or lower voice than yours can need a move of five or more semitones.
- Can it change a song from major to minor?
- No. Changing key moves every note by the same amount, so a major song stays major and a minor one stays minor. Turning major into minor means changing some notes and not others (the third, sixth and seventh of the scale), which a recording of the whole band mixed together does not allow.
- Can I slow down a song to learn it?
- Yes. Set the tempo to 50-75%, mark the passage with Set A and Set B, and press Loop: it repeats at that speed, in the original key, until you stop it. Raise the tempo step by step as you get it.
- Can it fix a recording that is slightly out of tune?
- For the whole recording, yes: type a number of cents, such as 30 or −15, to move everything up or down by that much (100 cents make a semitone). The page also measures how far the recording is from standard tuning and offers A = 440 Hz to bring it back. It cannot correct individual notes, as pitch-correction software does.
- What is A = 432 Hz tuning?
- Standard tuning puts the A above middle C at 440 Hz. Some musicians prefer 432 Hz, about 32 cents (a third of a semitone) lower. The A = 432 Hz button moves the whole recording down by that much, or by less if it measures a little flat already; an A = 440 Hz button appears when a recording measures off standard pitch, to bring it back.
- Does it work out the key and BPM by itself?
- It estimates both from the sound when a song opens, in your browser. The BPM is usually close for music with a steady beat but can come out at half or double the tempo people count (press ½ or ×2), and the key can be mistaken for its relative major or minor, which the page offers as the other possibility. Both are estimates, and you can type over them.
- Is my music uploaded?
- No. The file is read and processed in your browser, and the saved file is made there too. MP3, M4A and FLAC are written by an encoder that runs on this page.