I'm currently listening to a two-disc compilation album of Ricky Nelson. The guitar part (doubled on harmonica) that's at the very beginning (and repeated in a few other sections) of his version of the Gershwins' "Summertime" sounded familiar to me. I eventually placed it; I also know it from Johnny Rivers' version of Chuck Berry's "Memphis" (sometimes called "Memphis, Tennessee").
For the record, the part I'm talking about is E D B A G E. I'm unsure, but Rivers might slide into that initial E from a D note (that's the way I've always played it, at least).
Nelson's version of "Summertime" is from 1962; Rivers' version of "Memphis" was released in May 1964, so it's possible that Rivers took the guitar part from Nelson's "Summertime." That riff isn't in Chuck Berry's original, and I'd been wondering where it came from. However, while the chronology works out, I'm not sure if this was the case; I don't know much about Johnny Rivers.
I feel it worth pointing out that the bass part from Nelson's "Summertime" was copied by Blues Magoos for their "(We Ain't Got) Nothin' Yet," so there's a precedent of copying from it.
