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

Great post! Without question U2 Live at Red Rocks 05, June 1983! What an amazing experience that must have been for those who were fortunate enough to attend. U2 at their primal best (IMHO) just before they truly hit the map. Then they just got too popular and mainstream and got all weird on us...Too bad as early U2 man, that's just some DAMN GOOD music!

Stevie Ray Vaughan Aug. 1990 so I could tell him not to get on the helicopter!!!!
AC DC 1980 tour I was there had a fabulous time on acid but did not have to opportunity to really remember the music.
Robin Trower at a small club in Madison
Rory Gallagher anywhere any time!

Hawkwind at the Treorgy Tree Festival, 1988.
I didn't attend because of personal factors. They played all of my favourites, including Assault and Battery and others from Warrior on the Edge of Time.

Alternatively the Stax revue that toured England in 1967, and played in West Hampstead at a dive known as Kook's Clique. It was a revelation for both artists and audience; Otis Reading, Sam and Dave, Booker T were the house band, and they had only played segregated venues in the US before.
 Years later they would say
"Play it like we played in London"

Also my parents were there, two years before i came along,  so that gig is part of our family story

@kingbr, great point about catching a band early in their career, before they go mainstream and sell out (assuming they even get that opportunity). Not to mention having to deal with the trendster - wannabe, "Johnny come lately" fans that show up once the band becomes mainstream.

@sgreg1, you make two good points:

1) "SRV, so I could tell him not to get on the helicopter!"

Now that's the kind of creative response that I've been looking for in this thread!!

2) "I was there...but, I didn't have the opportunity to remember the music."

The first time I wrote down a setlist was on Springsteen's "The River" tour in 1980. I knew that he would play for 3 1/2 - 4 hours, so I figured that was the best way I could remember the show.

A few years ago, I discovered the website: "SETLIST.FM." This is a very helpful site, as I have found setlist's posted from shows that I saw all the way back to the 1970's!