This answer is on the right track; but, not surprisinigly, the rules have become more complicated in the Digital Age. Exactly when and how you are using copyrighted material can lead to differing answers.
Check Wikipedia or Google under "fair use - music" or "doctrine of fair use". Then go to the website for the Harry Fox Agency (www.harryfox.com). They still handle mechanical licenses, digital licenses, limited quantity licenses, etc. for most recorded and copyrighted music.
Bluesy Soul
