Interlude 3: Using Audacity to change tempo and pitch

So what I want to do here is show you how you can use Audacity to increase or to slow down the speed of a track without altering its pitch, or to increase or decrease the pitch of a track without altering the speed. What we first need to do is to select everything. If we go to the menu “Effect” you see that there are three things “Change Pitch”, “Change Speed” and “Change Tempo”. “Change Pitch” enables you to change the pitch without changing the tempo. You see that an F Blues can become any of those keys and without changing the tempo.

The next thing is to change the speed, but if you change the speed then you change both the tempo and the pitch. Generally speaking, that’s not what we want to do.

Let us, therefore, change the tempo. I am suggesting increasing it by about 30 per cent here - you can obviously vary it - in order to show you what the difference is. We select this and you see that the tempo is being changed.

What I will do then is use Quicktime to compare the old version with the new version to show you that, indeed, it has speeded up noticeably. Right, to do that we need to save it. I’m going to export it as a wav, because I am used to dealing with wavs. We’ll call this F Blues2.

You see here it is over on the right hand side. If I use Quicktime to play those two tracks, then you should be able to see the difference. Here’s the first version.

Here’s the faster version at the same pitch.

So what you will be able to use Audacity for, as I say, is to change the pitch without changing the tempo and to change the tempo without changing the pitch. That turns out to be very useful.