Basically, what you do is make a CD of your favorite tunes and drop it at a public location with a link leading back to the site so they know what it's about. Then they listen to it, and drop it somewhere else. Neat idea eh?
I can never figure out if musicians or the music industry is happy with "sharing" or not happy with copyright infringements. Or both. I suppose slapping a found CD in a CD player is reasonably safe, playing/inserting one in a computer drive seems fairly risky.