What the effect actually is
Two things at once, and the order matters. The song is played back slower than it was recorded, which drops the pitch with it — that dragging, heavier voice is not a separate effect, it is what slowing down does. Then the result is put through a room: a long reverb tail that keeps ringing after each note has stopped, so the gaps fill in and the track stops sounding like it is in a hurry.
Around 80% is where most of these sit. Below about 70% the vocal starts to sound underwater rather than slow, and above 90% the effect is there but nobody notices it. The strength slider moves everything towards untouched at once, which is the quickest way to find the point where it is obvious but not silly.
Why the pitch drops with the speed
Because that is the sound. It is possible to slow audio down without moving the pitch — there is a tool here that does exactly that, and it is the right one for a podcast or a lecture. It is the wrong one for this: a slowed track at the original pitch just sounds like the band playing badly, without the weight that makes the style what it is.
So this deliberately does what a record player does when you slow the platter, which is also what the first people making these were doing.
Getting a version worth keeping
Start from the preset and change one thing. Reverb is what most people overdo — past about 45% the words stop being words, and a track you cannot sing along to is not the one that gets replayed. A little bass helps because slowing a song down thins it out; two or three decibels puts back what the speed took.
The preview renders the whole track, so what you hear is exactly the file you will get. Everything happens on your own machine, which is also why a long track takes a moment on a phone.
Frequently asked questions
Why does it sound lower as well as slower?
Because slowing a recording down stretches its waves out, and longer waves are lower notes. That drop is the recognisable part of the style rather than a side effect — if you want the speed without the pitch, use the audio speed changer instead.
What speed should I use?
Between 75% and 85% for most songs. Slower than 70% and the vocal turns muddy; faster than 90% and the effect is barely audible. Ballads take more slowing than anything with a fast vocal.
Can I put it on TikTok or YouTube?
The file is yours to use, but the song is not — an edit of a copyrighted track is still that track as far as a platform’s content matching is concerned. Slowing it does not change who owns it.
How long does a full song take?
A few seconds on a laptop, longer on a phone, because your own device does the work rather than a server. There is no queue and no file size limit for the same reason.
Is my music uploaded anywhere?
No. The file is decoded, processed and encoded by the browser tab you have open. You can disconnect from the network after the page loads and it still works.
Something wrong with this tool, or an idea for it? Tell us