For a recent project, I needed to quickly listen to different music tracks, under some recorded voice-over I had. I decided to give GarageBand a try. I already had my music in iTunes, so setting up the project would be a snap.
I created a new project, dragged my music in from the media browser, and the VO (voice-over) in from the Finder… Easy, right? Well, there was just one problem. While the VO played fine, the music sounded slightly distorted, and slowed down. At first I couldn’t figure out why, but after a little digging, I realized the key was in the sample rate.
If you’re unfamiliar with sample rate, check out this definition on wikipedia. Basically, sample rate is one factor that determines the quality of you audio. The higher the sample rate, the better the quality, the lower that sample rate, the smaller the file. A standard audio CD uses 44,100 kHz, a DVD uses 48,000 kHz, and audio used on the web or on CD-ROM is commonly down-sampled to 22,050 kHz.
The music I was using was encoded at 48,000 kHz, as it turns out GarageBand is only capable of playing audio at 44,100… no lower, and no higher. The result, was my music sounded slow and distorted. Alternately, if you tried to play audio that was a lower sample rate, like 22,050, it would sound sped up in GarageBand.
This seems like a huge oversight by Apple…. making GarageBand so inflexible. There’s no good reason why GarageBand can’t look at the real sample rate, and play the track correctly.
Anyway, the solution is relatively simple. You must convert your audio to 44,100 if you want to use it GarageBand. You can do this by setting a sample rate of 44,100 in your iTunes preference and either re-encode from CD, or use the ‘convert…’ command, under the ‘advanced’ pull-down menu. You could also use the ‘Export to Aiff…’ feature in QuickTime.