I listened to the Beatles a lot in junior high and into high school. Now I'm not knowledgable on the how's and why's of music and music theory (that would be my brother!) but I always marveled at how their sound changed over time. From something boppy and fun to something mysterious and fun, with harmonies that are SO fun to sing along with (I'm looking at YOU, "Because").
They're very inspiring like that for me. Changing from awesome into...still awesome. Taking chances. But...chances for the masses, if that makes any sense. Doing their jobs, but in a way that they find interesting. Hmm...
Mental note: listen to more Beatles.