If you had access to a time machine, what concerts would you go back to see?

@boothroyd, good choice with Stephen Bruton. I wish I would've caught Gary Clark, Jr in the local clubs when I had the chance. I heard about The Shady Grove and Threadgills closing down. Man, it looks like the world is probably gonna be a boring place when things get back to normal. 

in the 50's sometime, my wife and I were in Montreal and noticed that Johnny Cash and his whole entourage was going to play at the Montreal Fair .....got tickets (cheap even in those days).... only sparsely attended....super great show.

Elvis, most any time, anywhere. If I had a time machine, let's go with the Million Dollar Quartet session at Sun. 

Beatles,  rooftop impromptu concert during Let it Be sessions.

Fleetwood Mac, anytime between '75  Fleetwood Mac album release and Tusk tour. 

Bob Seger, anytime after release of Night Moves album, preferably 1976-early 1980s

eagles hotel california tour, pink floyd (but after the breakup so it was only david gilmore, still great, sting w concrete blond -great opening band, elton john , aerosmith , jimmy buffet, james taylor(last 2 outdoors, something special about that, and  someone i imagine few of you have ever heard of-steve forbert in a little (400-500) seat venue. worst- tom petty(and i love his music)but so loud had to stand outside the auditorium doors to listen.

The Police at My Father's Place in Roslyn, NY, October 1979