Calling all linux/audio experts

Okay, some background information. I just got a gig installing linux on some guy's computer. I plan on installing Ubuntu to make it easy on me as well as him since I doubt he has any linux experience. He has given me some requirements that I must fulfill, but I'm totally stumped. Here's what he's asking for:

"An application that will provide me with high powered musical composition/editing/recording tools as well as midi interface (for guitar/dj turntables, etc.)"

Help me out guys. Thanks.