Change the tempo of your audio track with WaveShop

If you ever want to edit audio on Windows, the free GPL-licensed WaveShop would come up top on the list.

However, if you are trying to edit the tempo of your audio track using WaveShop, you would quickly notice that there is no such option (effect or plugin).

But it is possible (at least for MP3s) in a somewhat obscure way: changing the sampling rate.

I'm not an expert on acoustics, music or MP3; but a quick googling shows that the sampling rate is the number of samples of audio carried per second.

Thus, if you reduce your sampling rate to 80% (say 44100Hz → 35280Hz), it would make your MP3 player think that the samples in your file were taken at 28.34-microsecond intervals instead of 22.67 - a 25% "stretch".

So your track will actually play 20% slower, taking 2 min 5 sec if it was originally 1 min 40 sec. Exactly what we need!

To use WaveShop to change your audio track's tempo in this manner:

• open your track in WaveShop.
• go to Audio → Format....
• based on the tempo change you need (say x%), enter the correct Sample Rate value; note that if you want to slow down, x would be negative!

current sampling rate × (x/100 + 1)

• click OK.