1. He's "really rockin' in Boston, Pittsburgh P.A., deep in the heart of Texas, and out in Frisco Bay, all over St. Louis, and down in New Orleans": Chuck Berry
2. Rolling Stones drummer: Charlie Watts
3. He got "Behind Closed Doors" in 1973: Charlie Rich
4. Legendary blind pianist, soul singer, and owner of "Ray's Music Exchange": Ray Charles
5. He sang "Black Pearl" in 1969: Sonny Charles and the Checkmates, Ltd.
6. The most famous African-American country singer: Charley Pride
7. Detective mentioned in both "Searchin'" by the Coasters, and "U.S. Blues" by the Grateful Dead: Charlie Chan
8. That "Dirty Water": The Charles River
9. He walks in the classroom, cool and slow, he calls the English teacher "Daddy-O": Charlie Brown
10. Frequent caller to the "Pilot of the Airwaves": Charlie Dore
11. He felt like "Bustin' Loose":Chuck Brown and the Soul Searchers
12. A grandchild in the lyrics to "When I'm Sixty-Four": Chuck
13. Styx bassist who was one of two twins in the band: Chuck Panozzo
14. Their biggest hit was "The Devil Went Down to Georgia" in 1979: Charlie Daniels Band
15. Mexican-American guitarist who had a "Supernatural" album: Carlos Santana
16. Bird: Charlie Parker
17. Goofy '70s game show host who wrote Freddy Cannon's hit "Palisades Park": Chuck Barris

Bonus: The third group mentioned in "Life is a Rock (But the Radio Rolled Me)" by Reunion (and they have nothing to do with the answer to Question 4): Ray Charles Singers