First would have been Tower of Power opening for Santana in 1970. A weird, low ceilinged, cement convention space at Cal Expo, long, long before they built an ampitheater there. Third show was in that same space, Loggins-Messina opening for Elvin Bishop and Stoneground. I would have been 13 for the first, maybe 14 for the 2nd. 15 for the Dead at Sacramento Memorial in '72. But the most revelatory was probably the Mahavishnu Orchestra playing 2nd bill to Emerson, Lake, and Palmer the year after. I had never heard of them. How on earth does a three piece band follow that?