From a fine piece in The New York Sun:
By the early 1950s, Mr. Domino had perfected the basic beat of New Orleans rock 'n' roll: repetitious 16th notes in an insistent triplet pattern.Virtually everything he played, fast or slow, conformed to that motif, which made ballads and rockers alike irresistibly danceable. It was the big beat. Mr. Domino's best music was harmonically simple too. "My Girl Josephine," for example, essentially consists of three chords (B flat, D sharp, and F) over and over in the I-IV-V pattern of the blues.
Read the whole thing.