How to change the tempo of a song
- Choose an MP3, WAV or M4A file up to 10 minutes long.
- Check the Original BPM. We detect it for you, and you can type over it if you know the real tempo.
- Type the New BPM you want, or switch to Speed % and use the slider.
- Leave Keep pitch on to change only the tempo, or pick Change pitch with speed for a sped up or slowed down sound.
- Press Change tempo, compare it with the original, then download the WAV.
Tempo vs pitch: what actually changes
Speed and pitch are tied together in recorded sound. Play a record faster and every note goes up, because each wave now passes by more often. A song sped up by 10% ends up about 1.65 semitones higher, and doubling the speed raises it a full octave. That’s what the Change pitch with speed option does. It simply plays your audio back faster or slower, so nothing gets chopped up or smeared.
Keep pitch uses time-stretching to pull the two apart. The audio is cut into short overlapping slices of about 46 milliseconds. To slow down, slices are spaced further apart in the output; to speed up, closer together. Each slice is picked from a small window around where it should come from, at the exact spot where its waveform lines up with the slice before it, so the joins don’t click or warble. This method is called WSOLA, and it’s the same family of technique many DAWs use for their basic stretch mode.
Which setting should you use?
Use Keep pitch when the song has to stay in key: matching a sample or an acapella to your beat, practicing a part at a slower tempo, or lining up two tracks in a DJ set. Use Change pitch with speed for nightcore and sped up edits, slowed versions, or whenever you want the cleanest possible sound, since it doesn’t chop anything up. For slowed versions with reverb already on, the slowed + reverb maker does it in one step.
Working out the speed for a target BPM
The speed is just the new BPM divided by the old one. Going from 90 to 100 BPM is 100 ÷ 90 = 111.1%, and taking a 128 BPM house track down to 120 is 93.75%. You don’t need to do the math here, since typing both BPMs sets the speed for you, but it helps to know that a 5% change is barely noticeable while 20% or more changes the feel of a song. If you don’t know the original tempo, the BPM and key finder will tell you, along with the key.
FAQ
How do I change the BPM of a song without changing the pitch?
Choose your file, type the new BPM, leave Keep pitch selected and press Change tempo. The tool time-stretches the audio, so it gets faster or slower while every note stays in the same key.
Is this BPM changer free, and is my song uploaded?
It’s free with no sign-up and no watermark. Your song is never uploaded: it’s decoded, processed and turned into a WAV inside your browser, so the file never leaves your device.
What files can I use?
MP3, WAV and M4A work everywhere, and most browsers also open FLAC, OGG and AAC. Files can be up to 10 minutes long. The download is a 16-bit WAV at the same sample rate as your original.
How far can I speed up or slow down a song?
Anywhere from 50% to 200% of the original speed. With Keep pitch on, changes between about 80% and 125% sound the most natural. Bigger jumps work, but drums can start to sound a little soft or doubled, which happens with any time-stretch.
Why is the detected BPM half or double what I expected?
Tempo detection hears the strongest repeating pulse, and in a lot of music that pulse could be counted two ways. A trap beat at 140 BPM can also be counted at 70. If the number looks off, tap one of the half or double suggestions, or type the BPM you know into Original BPM.
Does it work on iPhone and Android?
Yes. It runs in Safari, Chrome, Edge and Firefox on phones and computers. On an older phone, long songs take a few extra seconds to process.