Slow down audio
Hear every note of a fast passage, in the same key, on your own device.
- Nothing is uploaded
- Works offline after first use
- Open source
- No watermark · limit is your device’s memory; phones hold less
Slow down a song, solo or language recording to learn it, keeping the pitch. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after your first run to save itself for offline use, and then it works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
Musicians slow a recording down to learn a solo, and language learners do it to catch every word. Starting at 0.75×, this page makes a slower copy in the same key, so you can play along on your instrument without retuning.
A worked example: a guitar solo that runs from 2:10 to 2:40 in a song lasts 30 seconds; at 0.75× it lasts 40 seconds, and at 0.5× a full minute. Cut the solo out first with Trim audio so you are not waiting through the verses, then slow just that part. Practise at 0.6×, move up to 0.75× and 0.9×, and play with the original when the notes are under your fingers.
Because the key is kept, a song in E stays in E, and your tuner still agrees with the recording. If the recording itself is tuned slightly flat, as many older records are, move the pitch slider by one semitone to meet your instrument instead of retuning it. For the dreamy slowed-and-reverb sound, tick the option that lets the pitch drop with the speed instead.
For language study, 0.8× is often enough to separate words a fast speaker runs together, without making the voice sound unnatural. Save the slower copy as MP3 to play on a phone, or WAV if you will cut it into phrases in an editor. The file stays on your device.
How it works
- Drop one or more songs or recordings.
- Pick a speed below 1×. Leave the pitch at 0 to stay in key, or shift it to match your tuning.
- Run it and download the slower copy.
In your browser, not on a server
Your browser’s own audio decoders read the file in the tab. The speed is changed with WSOLA (waveform-similarity overlap-add): the sound is cut into overlapping 43 ms windows, spread out or packed together, and each window is nudged to line up with the one before so there are no clicks. The pitch is then moved by resampling through a windowed-sinc filter, which also shortens or lengthens the sound, so the stretch is sized to leave exactly the speed you asked for. The result is written with the same encoders as the audio converter.
Compared with upload-based tools: Online pitch shifters upload the whole song or recording and many cap the length or the number of files on a free plan. Here the file never leaves your device, a whole album can go in one batch, and nothing is added to the sound.
Verify it yourself. Give the page a short while after your first run to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Will it stay in tune with my guitar?
Yes. Slowing down keeps the pitch unless you tick the option to let it follow the speed. If the recording itself is tuned a little off, nudge the pitch by a semitone rather than retuning your instrument.
How slow can it go?
Down to 0.5×. Below about 0.7×, drums and sharp attacks start to sound soft or doubled, which is normal for any time stretch. Sustained notes, voices and guitar lines hold up much better than percussion.
How do I make a slowed and reverb version?
Tick “Let the pitch follow the speed” and choose 0.8× to 0.9×: the song drops in key as it slows, like a record played at the wrong speed. This page adds no reverb, so put the slowed copy into an editor or app for that last step.
Can I slow down a YouTube video I am learning from?
YouTube’s own speed setting already slows playback while keeping the pitch. Use this page for files you have on your device, such as a lesson recording, a voice memo of a teacher, or a practice track, when you want a slower copy to keep.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after your first run to save itself for offline use; then you can turn off Wi-Fi and it still works.
More video and audio tools
Pitch and speed changer
Change the key of a song, or play it faster or slower, keeping the other the same. Done on this device.
Crop video
Cut away the edges of a video, or crop it to vertical or square for social media. Cropped on this device, never uploaded.
Change video speed
Make a video faster or slower, with sound that stays at the right pitch. Done on this device, never uploaded.
Merge videos
Combine clips into a single video, in the order you choose. Done on this device, never uploaded.