I saw a concert a couple of years ago with a lineup of various bands (Chicago, America etc) and one of the beach boys (I think Mike Love? played keyboards and sang) and it was a fantastic performance, just couldn't get enough of it. Dare I even say, his set brought upon the biggest excitement amongst the audience. He had some back up male singers helping out with the high bits.
As for Chicago, I was disappointed- no angry

that the lead singer wasn't there and a replacement sang all the songs. And Peter Frampton spat the dummy because the crowd wasn't getting into it \touchy/