Donaldson R F Change Audio Speed
Play a recording faster or slower. Choose the speed, decide whether the pitch should change with it, listen, and save the result.
Tempo, pitch and speed
There are two ways to change speed. Keep the pitch stretches or squeezes time without making voices sound higher or lower, which is what you want for speeding up a lecture or podcast, or slowing down a song to learn it. Change with the speed is the old record-player effect: faster is higher and shorter, slower is deeper and longer (a 2× speed raises the pitch by one octave, 12 semitones).
Changing the pitch along with the speed is done instantly in your browser. Keeping the pitch uses the ffmpeg conversion engine (about 31 MB), which is downloaded only when you press the button and kept by your browser afterwards. The preview uses your browser’s own player, so it follows the pitch option too. To cut out a section first, use the MP3 cutter; to change volume afterwards, change the volume. The engine is ffmpeg.wasm, open-source software.
Frequently asked questions
How far can I change the speed?
From a quarter of the speed to four times the speed. Very extreme values make speech hard to understand.
Why is the preview different from the saved file?
The preview is your browser’s live playback; the saved file is processed by a separate algorithm. The tempo is identical, and the sound quality of the saved file is normally the better of the two.
Is my file uploaded?
No. Everything runs in your browser.