Using store music to attract shoppers under 33 1/3 years old

I am a veteran as "music poobah," having navigated the early period (when we played tapes in the store), middle period (when we realized that paying for a music service that handled all BMI/ASCAP/etc. clearances was cheaper than paying for direct licenses), and current (satellite radio, from DMX through a local supplier). There are things about it I like, and others I don't like, but I'm convinced that having music helps set a positive and welcoming tone for our store.

Also, staff complain about music, but they complain more when it isn't there (recently tested by equipment that froze for several days).

I walked out to the floor from our offices 15 minutes ago, and noted that the Gladys Knight & The Pips version of "I Heard It Through The Grapevine" was playing. Great song, recognizable version, and ... I want to make sure the store feels welcoming for students who're new to town.

This might be their grandparents' favorite song, or possibly their parents, but (most likely) it isn't theirs. Among the channels that I have programmed are ones called "College Rock," "Adult Alternative," and "Acoustic Crossroads." The second of those played this afternoon, and I made a note to myself that it was "too shreddy" at times (e.g. shredding on guitar that wasn't very musical). Now I'm worrying about "Mo' Soul."

I think that there's a benefit to playing a variety of music. But what has helped you make your store welcoming and attractive to the ears of people who're younger (e.g. under 33 and a third)?