AudioKit

Audio speed and pitch changer

Speed up a lecture without the chipmunk voice, slow a song down to learn it, or move a track up or down a few semitones.

  • Runs on your device
  • No upload
  • No sign-up
  • Free

Open a song, lecture or voice note

Stays on this device: nothing is uploaded. You can also drag a file here or paste it.

Speed and pitch are linked on tape, not here

Play a tape or record faster and everything rises in pitch: speed and pitch are the same thing, because the wave simply passes by quicker. Double the speed and the pitch goes up exactly one octave (12 semitones); in general the shift is 12 × log₂(speed) semitones.

Digital time-stretching breaks that link. It cuts the audio into overlapping slices of a few tens of milliseconds and lays them closer together or further apart, choosing the overlap so the waveforms line up. Pitch stays put; only the timing changes. To shift pitch alone, AudioKit resamples (which changes both) and then time-stretches back to the original speed.

Questions people ask

How do I speed up audio without changing the pitch?

Leave “Change pitch with speed” unticked and set the speed. AudioKit uses ffmpeg’s atempo filter, which stretches or squeezes time in small overlapping chunks so voices keep their natural pitch.

How do I change the pitch without changing speed?

Set speed to 1× and move the pitch slider. Each step is a semitone; +12 is an octave up. It’s useful for transposing a backing track to your vocal range.

What speed is best for lectures and podcasts?

Most people follow speech comfortably at 1.25–1.5×. Above 2× comprehension drops for unfamiliar material.

How do I make a slowed + reverb or nightcore version?

Tick “Change pitch with speed”. Slowed versions use around 0.8–0.85×; nightcore uses about 1.25–1.35×. Reverb isn’t included.

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