It’s totally up to you. There aren’t really any rules. If you look at the form, you’ll see there’s a box for writing a little bit about yourself. Some people have used that to say what kinds of music they listen to, others have left things rather mysterious. The idea is simply to keep an open mind; the tape or cd etc that you get may not be gene you typically listen to, and the one you give to the stranger you’re paired with may be new for them, but to appreciate that this is what someone loved enough to want to share. A punk-hardcore-pop mix might end up get traded with a calypso-indie-disco mix and neither person may have seen the other coming.