from Wikipedia:

"What'd I Say" (or "What I Say") is an American rhythm and blues song by Ray Charles, released in 1959. As a single divided into two parts, it was one of the first soul songs. The composition was improvised one evening late in 1958 when Charles, his orchestra, and backup singers had played their entire set list at a show and still had time left; the response from many audiences was so enthusiastic that Charles announced to his producer that he was going to record it.

After his run of R&B hits, this song finally broke Charles into mainstream pop music and itself sparked a new subgenre of R&B titled soul, finally putting together all the elements that Charles had been creating since he recorded "I Got a Woman" in 1954. The gospeland rhumba influences combined with the sexual innuendo in the song made it not only widely popular but very controversial to both white and black audiences. It earned Ray Charles his first gold record and has been one of the most influential songs in R&B and rock and roll history. For the rest of his career, Charles closed every concert with the song. It was added to the National Recording Registryin 2002 and ranked at number 10 in Rolling Stone's "The 500 Greatest Songs of All Time".