Roy Byrd, aka Professor Longhair, New Orleans legend, who had a series of regional hits in the '40s and '50s. The New Orleans/Louisiana piano players who became bigger later on (Fats, Dr. John, Little Richard, Jerry Lee Lewis) drew heavily from his style. As a teenager, Dr. John was the guitarist in the Professor's band. His voice cracked, he whistled, and yodeled, and kicked the side of his piano for percussion, so he was a little too edgy for white audiences in the day and never broke through outside N.O. until very late in his life, when Dr. John started playing more and more of Longhair's music and Ol' Roy got a recording contract and a regular gig at Tipitina's, a restaurant and bar named after one of his early local hits. He won a Grammy posthumously for an album with Dr. John in the band, once again playing guitar. I love Professor Longhair. If you're in the U.S., a current commercial campaign for Coca-Cola about hamburgers has this song in the background.
P.S. As I think about it, this entry could fit two of the three categories. So I'm going to figure out which one to stick it in after I do more songs! Make it Theme 1, since Professor Longhair was a N'Awlins legend.