Roger McGuinn

First the "Jingle-Jangle" and basically the birth of Folk-ROCK with the first two albums by the Byrds. Then his guitar in "Eight Miles High" and essentially the birth of "American Psychedelic Folk." Of course, there would also be the exclusion of Crosby's "Triad" from "The Notorious Byrd Brothers" and the group's collapse starting in mid-1968, but I feel generous...