I generally buy a CD on spec only if I know something about the repertoire, which means I'll buy CDs by completely unknown performers if they're singing songs I know and like, especially songs I would like to learn. I definitely prefer Trad stuff when I don't know the performer; way too many self-indulgent w***ers present themselves as singer-songwriters in the folk idiom! I'll buy a CD of original (i.e., composed by the performer) material only when I've heard it played on the radio or in concert, or if a friend whose taste I trust recommends it.