I do a TON of music prep with recordings and my iPod is an indispensible tool for this. Just today I was prepping for a vocal harmony part I have to record in the studio on Wednesday. (Nothing terribly fancy here - a friend's basement studio, but it's a VERY capable studio - I'll probably record my vocals in a sound treated room with an AKG C414 going through an Avalon preamp and being mixed in Digital Performer) I also record things in my own home studio and critque them while driving, and I listen back to the board feed recordings from the Sunday services to critique what I did on the drums with the praise band. I also listen to songs I need to know for upcoming gigs. I've become a big believer in recording and listening to your recordings and other music as a means to learn and prep music. I have an hour commute each way and I try to make the most of it.