I'm a newbie to Garageband and I'm trying to record a vocal track using my external mic. The mic (a Shure BG 3.1) is plugged into my Audiobox USB box, which is connected to my MacBook Pro, but GB isn't registering any signal from the mic. I can hear my voice coming through the mic into my headphones, but there's nothing coming through on Garageband. And the Audiobox worked fine recording midi. Can anyone help? Is it my weird mic? Or is there something really simple I'm missing?