Change the tempo of audio without changing the pitch

Open your file, choose Effects ▸ Time/Pitch ▸ Time Stretch…, keep the mode on Preserve pitch and set a new length. Slower audio gets longer, faster audio gets shorter, and the pitch stays where it was. Auditius does it in your browser, without uploading anything.

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The spectral view of a mix in the Auditius editor, with frequencies from 0 to 20 kHz over time

How to change the tempo of a song or recording

The Time Stretch window opens as soon as your file has loaded.

  1. Click Open a file to stretch, or use File ▸ Open… (Ctrl+O), and choose your audio file.
  2. To change only part of the file, select it first. With nothing selected, the effect applies to the whole file.
  3. Open Effects ▸ Time/Pitch ▸ Time Stretch… from the menu bar.
  4. Leave Mode on Preserve pitch (time stretch).
  5. Set New Length. 200% plays at half speed and 50% at double speed; the Half Speed and Double Speed presets do exactly that.
  6. Press Preview to listen, then click OK.
  7. Export the result with File ▸ Save As… in the format you need.

How to work out the new length

New Length is a percentage of the current duration, so it works the other way round from a speed control. To go from one tempo to another, divide the old tempo by the new one and multiply by 100.

From 120 to 100 BPM: 120 ÷ 100 = 1.2, so set 120%. From 90 to 100 BPM: 90 ÷ 100 = 0.9, so set 90%.

  • About 10% slower: 111%.
  • About 10% faster: 91%.
  • 25% faster: 80%.
  • The range goes from 25% to 400%, up to four times faster or slower.

Tips for clean results

Time stretching always rebuilds the audio, so a little care pays off.

  • Small changes sound best. A few percent is usually transparent; extreme settings add artifacts, most audibly on drums and other sharp attacks.
  • Stretch once. Several small passes in a row degrade the sound more than one pass with the final value.
  • To learn a fast passage, slow it to around 125% to 150% and repeat it with Options ▸ Loop Mode (Ctrl+L).
  • If you want the pitch to follow the speed, like a turntable or tape machine, choose Resample (changes pitch) in Mode, or try the Tape Slowdown preset.

Related tools: pitch and tempo in the multitrack

Effects ▸ Time/Pitch ▸ Pitch Shift… does the opposite: it changes the pitch by semitones and cents and keeps the length. Use it to move a song to another key or to tune a sample to your track.

Effects ▸ Time/Pitch ▸ Pitch Bender… changes the pitch over time along a curve you draw, with presets such as Tape Stop and Spin Up.

In the Multitrack view you rarely need to stretch by hand. Set the session tempo with Options ▸ Session Properties (Tempo)…, give a file its original tempo with File Tempo… in its right-click menu, and turn on Follow Session Tempo for the block. Auditius then stretches it to the session tempo, and Options ▸ Tempo Map… lets the tempo change during the song.

Frequently asked questions

Will the pitch change when I slow audio down?

Not with Preserve pitch (time stretch), which keeps the original pitch. With Resample (changes pitch), slower audio also sounds lower, like a tape played slowly.

How do I change the BPM of a song?

Divide the original BPM by the target BPM and multiply by 100, then use that as New Length. Auditius does not detect the BPM for you; for loops made of whole bars of 4/4, Guess from length in the File Tempo window can estimate it.

Can I speed up a podcast or voice recording?

Yes. A New Length of 91% makes it about 10% faster with the same voice pitch. Preview first: speech tolerates moderate changes well.

Is there a limit on how much I can stretch?

New Length goes from 25% to 400% in one pass. Larger changes are possible by applying it again, at a cost in quality.

Does my file leave my computer?

No. Time stretching runs in your browser, in a background worker on your own device, and nothing is uploaded.

Audio tools