1. "I'll Feel a Whole Lot Better" 2. The jangling sound Roger McGuinn got from his 12 string Rickenbacker. You can draw a straight line from that sound to Tom Petty. 3. "Sweetheart of the Rodeo", an album guided by Gram Parsons during his relatively brief time with the band. It is generally considered the birth of country rock.
This one is an interview from guitar.com in which McGuinn discusses his guitar sound and construction. It's 11 minutes long and probably more than most non-guitarists and non-musicians want to know. The video is also goofy. Personally I found it fascinating. It always interests me to listen to visionaries and difference makers, no matter what their line of work is.
From a recent Super Bowl halftime show. Billed as a Tom Petty performance, this song is more of a Mike Campbell performance. Not taking anything away from Campbell but I hope he sends Roger McGuinn a cut of his royalty checks.