As the frontman of the Byrds, Roger McGuinn and his trademark 12-string Rickenbacker guitar pioneered folk-rock and, by extension, country-rock, influencing everyone from contemporaries like the Beatles to acolytes like Tom Petty and R.E.M. in the process. James Joseph McGuinn was born on July 13, 1942, in Chicago, where by his teenage years he was already something of a folk music prodigy. After touring with the Limelighters, in 1960 he signed on as an accompanist with the Chad Mitchell Trio, appearing on the LPs Mighty Day on Campus and At the Bitter End; frustrated with his...