Audio / Tempo
Audio Speed Changer (Keep the Pitch)
Speed up or slow down any song, podcast, or recording without making voices higher or lower, or change the pitch in semitones without changing the speed, and download MP3 or WAV.
Audio Speed Changer (Keep the Pitch): Speed is changed with time-stretching (WSOLA): the sound is cut into short overlapping slices, about 46 milliseconds each, which are spaced further apart or closer together and lined up so their waveforms join smoothly, so the length changes but the pitch stays. A pitch change stretches the sound and then resamples it, which moves the pitch while keeping the length. Tested on pure tones, the length comes out exact and the pitch unchanged to within 0.01%. Runs 100% locally in your browser with zero server file uploads.
- Category
- Video tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
MP3, WAV, M4A, OGG, or FLAC · nothing uploaded
Speed and pitch are separate: the speed changes without making voices higher or lower, and the pitch moves in semitones without changing the length. Large changes, below 70% or above 150%, add some smearing, as with any time-stretching.
Your file is processed in your browser and never uploaded. MP3 files are encoded with LAME, free software under the LGPL, loaded as a separate file; its source is at lame.sourceforge.io.
Practising with slower audio
Musicians slow a recording to 70–80% to learn a fast passage and bring it back up step by step; language learners slow down speech the same way. Keeping the pitch means the song stays in the key you play along in.
To cut out the part you are practising first, use the audio trimmer; for video, the video speed changer.
Changing the key
Moving a song down two or three semitones puts it in a more comfortable range for many singers; moving it up by one fixes a recording that was played slightly flat. Changes of more than about four semitones start to make voices sound unnatural.
How to use it
- Choose an audio file from your device.
- Set the speed, from half to double, and the pitch, if you want to change it.
- Apply, listen to the result, and download it as MP3 or WAV.
Privacy & limitations
Your audio is processed in your browser and never uploaded.
Related tools
Frequently asked questions
Why does very slow or very fast audio sound smeared?
Time-stretching repeats or skips tiny slices of sound; beyond about 70% or 150% the joins become audible, especially on drums and speech consonants.
How is this different from slowed and reverb?
Slowed edits lower the pitch along with the speed on purpose; this tool keeps the pitch, as a music teacher or a podcast listener usually wants.
How many semitones is a key change?
Each semitone is one step on a piano; +2 moves a song up a whole tone, and ±12 moves it a full octave.
Free tool · runs in your browser · no account required