# Change Speed

### From Audacity Manual

Use the Change Speed effect to change the speed of a track, affecting its tempo, pitch and frequency content. When you slow a track down, all its frequencies become lower, and when you speed it up, they all become higher.

To change the tempo of a track without affecting its pitch or frequency range, use Effect > Change Tempo... or Effect > Sliding Time Scale / Pitch Shift....

  Accessed by: Effect > Change Speed...

The Percent Change input box, slider and Standard Vinyl RPM drop-down menus are all linked: changing one will change the others.

## Percent Change

If you know how much you want to change the speed of the audio in percent, enter that value here. You can also drag the slider to choose a Percent Change - the input box will update as you drag the slider.

If you know the original length of the selection and its target length, you can calculate the percent speed change thus:

  ( ( (original length) - (target length) ) / (target length) ) * 100 = percent change

For example, if the selection is 3 minutes 21.73 seconds and you need it to be 3 minutes 15 seconds, the calculation is:

  original length = 201.73 seconds, target length = 195 seconds
  ((201.73 - 195) / 195 ) * 100 = 3.451%

The calculation works the same if you want to lengthen the selection, just enter the resulting negative value.

## Standard Vinyl RPM

If you have a recording of a record that was played back at the wrong speed you can correct that using these two drop-down menus. In the from drop-down choose the speed the record was played back at; in the to drop-down choose the speed is should have been played back at.

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