I wish I could remember a life-changing concert from my youth! I lived in Dayton, OH as a teen during the 60's and it wasn't exactly a hot destination for the top groups of the time. I cut my teeth on surf music, which my first band was deep into when the British invasion occurred and turned our heads and minds. At the same time, folk music was exploding on the mainstream radio stations and everything seemed to change overnight.
I did attend a really good concert by none other than Simon and Garfunkel. When I went off to college, things improved:
Philadelphia: Leslie West and Mountain; The Turtles (ha, ha remember them?); Spencer Davis Group; The Rascals; Nazz
Kent State University: Emerson, Lake and Palmer (the best concert I recall attending); lots of folk types like James Taylor, John Hartford, Joan Biased, etc.
For the life of me, I know I went to many others, but can't recall them! They all impacted me and my playing, but none of them changed my life significantly. If you can remember the 60's, you really weren't there!