Hi everyone. I’m new to GarageBand, and would really appreciate it if someone could explain how I could record vocals and piano (or guitar) at the same time on my MacBook, using my Focusrite 4i4 for the instrument and my Samson C01U Pro USB mic (which, unhelpfully, can’t plug into the Focusrite). I’ve tried creating an aggregate device, but didn’t understand the parts about the word clock and so forth. Or is it simply not possible, and I'll need to buy a non-USB mic to hook up to the Focusrite? Thanks in advance!

Hi - - First, set up the Aggregate Device as shown in the screenshot below (ClockSource = Inteface, DriftCorr on for USB Mic) - Note which channel represents the USB mic in the Aggregate Device (in the example ch 15) - Select the Aggregate Device as the Input when you create a new Project or in GB Preferences > Audio - Select the appropriate input channel (Shortcut "B") for each audio track (in the example Track 1 for Gtr, track 15 for USB mic) - Configure the Track Headers (Option-T) to show the Record buttons - Record-arm both tracks - Record! You could also check out video #4 in the GB course linked above re selecting the Input source..