GarageBand can do many, many things, but today I’d like to walk you through how you can use it to change the pitch of an MP3 file.
This can be useful for transposing the key of a recording that you are trying to learn. Many times there is a perfect ‘ukulele key for a song and it’s not always the same as what was recorded. For instance, I’m Yours by Jason Mraz is recorded in the key of B, but most people play it in C on the ‘ukulele. With GarageBand you can move the key of the recording up a half step into the key of C so that you can play along.
First of all, you need GarageBand for OSX. The one for iPad or iPhone doesn’t do what we need it to do. If you are on PC, you can do a similar thing in Audacity, but the process will be slightly different.
How to Change the Pitch of an MP3
The first step to changing the pitch of an MP3 is to open GarageBand and create a new blank project file. Delete all existing tracks if you start with a template (click to highlight then press “command” and “delete”).
Open the OSX Finder in front of the GarageBand window and locate the track you want to transpose. Click, drag, and drop the track into the dark-grey center of the GarageBand window.
The cursor will get a little green plus sign next to it to show that you can move the file there. This creates a new track from the imported song with an orange waveform.
Once the song loads it looks like:
Turn off the metronome. It’s just going to be confusing unless you know exactly what BPM the tune is. Go to the Control menu and uncheck the metronome box. Or click the metronome box in the control bar to the right of the heads-up display.
With the track selected, open up the track info. Click on the “i” icon in the bottom right corner. This is where you can start adding effects to the track for pitch shifting.
Then click from “browse” to “edit” under the track image. You should see a “rack” of effects like “noise gate” and “compressor.”
Click on an empty effect slot. This will bring up a drop-down with many effect options. Scroll down to the second section called “Audio Unit Effects” and click on the one called “AUPitch.” This loads a pitch shift effect that can transpose the track.
Click on the effect image to edit the settings. This will bring up a little window with four “knobs” – Pitch, Effect Blend, Smoothness, and Tightness. I usually adjust Effect Blend, Smoothness, and Tightness to 100%.
Adjust the Pitch knob to transpose the song up or down. It is measured in cents which is a bit counter-intuitive, but it’s simple once you know the conversion.
100 cents is one half step. If you wanted to move a song in A up to B, you’d go up two half steps – or 200 cents. Remember that the further you go, the weirder it sounds. If you like hyper chipmunks or slow motion robots then by all means, crank that dial!
Play back your song and the pitch shifting will transpose everything you hear. To turn the AUPitch off, just click the light blue button to the left of the effect slot.
If you need a quick an dirty way to change the pitch of a song, Garageband can do the trick. However, in recent years I’ve been using Anytune to do this same thing. It’s a fabulous piece of software that is easier to use than Garageband for this purpose and renders cleaner tracks even when transposing long distances. You can also slow down a song and solo out instruments using their magic spectrum analyzer. Highly recommended.