Pacific Gas and Electric opened for John Mayall at the Kinetic Playground (Aaron Russo's Electric Theater) in Chicago around 1969 and came out smokin'. I don't remember Mayall's lineup of band members at the time but do remember him being upset with the bass player's volume. PG & E went on to return many times, gathered a loyal following and never had a bad night any of the many times I heard them.
'they blew'em off the stage'
what concerts have you attended, where the warm up act blew the headliners away.....my examples...brownville station upstaging zz top to the point where people where chanting 'brownsville station!' during the littl ol' band from texas' set.....another..t.rex upstaging lynyrd skynyrd(yes there really was such a show), and the grass roots upstaging cream.