Homeoke

How to change a song's key without changing its speed

Last updated 25 August 2026

A song written for somebody else's voice is not a song you cannot sing. It is a song in the wrong key. Moving it is a small operation with a few things worth understanding, chiefly how far you can push it before it starts to sound wrong.

Why pitch and speed used to move together

Play a record faster and it goes up in pitch. Play a tape slower and it goes down. The two were locked together because the recording was the physical motion: change how fast you read it and you change both at once.

Digital audio inherited the same behaviour for the same reason. Read the samples faster and you get a song that is both higher and quicker: useful for a chipmunk voice, useless for singing along, because a song two semitones up is also several beats per minute too fast, and you cannot follow it.

What a pitch shifter does instead

Modern pitch shifting separates the two. The usual approach, a phase vocoder, chops the audio into short overlapping slices, works out what frequencies each slice contains, moves those frequencies up or down, and puts the slices back together at their original spacing in time.

Because the slices go back where they came from, the song lasts exactly as long as before. Because the frequencies inside each one have moved, it is in a different key. The tempo does not budge.

This is not free. Rebuilding the audio from a description of its frequencies loses a little, and the further you move it the more obvious that becomes. Which brings us to the practical question.

How far can you move a song?

In semitones, from the original:

• One to three: essentially transparent. Most listeners would not notice if you did not tell them.
• Four to six: audible if you listen for it. Cymbals and hi-hats are the first to give it away, taking on a slightly watery, smeared quality. Perfectly usable for singing along.
• Beyond six: the character of the recording starts to change. Voices and drums sound synthetic, and the result is more of an effect than a transposition.

Homeoke allows six semitones in each direction, which is deliberate rather than arbitrary: half an octave in either direction covers every practical singing decision, and past that the artefacts are worse than the problem being solved.

One useful thing to know: if a song is more than about five semitones away from where you need it, try moving it the other way instead. Down five is often a better result than up seven, and it may put the melody somewhere your voice is happier anyway.

Finding the key that suits you

There is no formula, but there is a fast method.

1. Start at nought and sing the chorus. The chorus, not the verse, because the verse is almost always the easy part, and a song you can start is not the same as a song you can finish.
2. Notice which end hurts. Straining at the top means come down. Losing the bottom notes into a mumble means go up. Both at once means the song is wider than your range and no key will fix it, so pick which end matters more and accept the other.
3. Move two semitones at a time. One is hard to hear; two is a real change. In Homeoke you can do this while the song is playing, so you do not lose your place.
4. Then move one back. Singers almost always overshoot on the first pass. Nudging back a semitone from "definitely comfortable" often lands on the version that sounds best, because the top notes are where the interest is.

Homeoke also shows you the range the song asks for, measured from the original singer's own vocal, and that range moves with the key control. You can watch a song come into your range as you shift it, rather than guessing.

Key change and vocal removal together

These two operations are what make an ordinary audio file usable as a backing track. Taking the singer out gives you something to sing over; moving the key makes it something you can sing over. In Homeoke both run on the phone, in the right order, while the song plays: the separation happens first and the key shift is applied to what comes out, so you are never pitching the original singer up along with the band.

You can change your mind mid-song and it takes effect immediately, which matters more than it sounds: the wrong key is usually only obvious once you are already singing.