Absolutely insane vocals from John here. Carl's face at the end says more than a thousand words.

Ahh, what I wouldn't give for Johnny to play more rock when he was at his best. He had all the predispositions for it, as for any genre, with a voice like that there is little that can be a challenge. But specifically in the rock formula, his voice worked extremely well. If you still don't believe me despite the above recording, find the duet with Bob Dylan "that's all right, mama", or matchbox with Carl and Clapton live from the Johnny Cash TV show. If you STILL don't believe me, try "rock n roll ruby", "call me the breeze", "you're my baby" or "down the line".