You may have a source of music you weren't aware of: DVDs. A full-length audio track from a DVD may not be desirable, but the extra tracks from a bonus DVD are perfect.
Case in Point: Simply Red's Home. The bonus DVD has four tracks, two excerpts from a full-length live DVD and two non-album tracks.
Use an application to rip the audio from the DVD. I use and recommend Audio Hijack for the Mac from Rogue Amoeba Software. You should rip to AIFF to get the best quality. If you click record just before you select a track from the DVD menu, then stop recording after, you'll get individual tracks instead of a long stream.
Drag all the AIFF tracks into iTunes, tag them, then rip to AAC or preferred file format. Keep the AIFFs somewhere outside your library as you may need to re-rip them at a later stage.
The procedure above is highly simplified but is intended to demonstrate that it can be done fairly simply. There are often DVD tracks well worth listening to as audio tracks.