I wasn’t looking for a psak and would certainly ask before doing so, it was just something I always wondered about. Also if this happened often, it would probably shut down the whole music business. Its not uncommon for people to copy recipes for personal use from a cookbook to keep things clean. If two people shared the cost of a cookbook, can each one copy recipes for personal use?
Joseph, the difference (as I see it) is that an mp3 is a physical thing which cant be copied or shared. As far as the book, see my example above.
DY, is a penny considered as having the same value Halachically as $8?
Again, not looking for a final answer, just thought it was an interesting question.