A combination of an ice cream social and some sort of music event. Idea can be applied to almost anything that makes a concert something to talk about to a person who doesn't have to like the band playing.
i.e. "I went to a Weezer concert last saturday," said John.
"I don't really care for Weezer,"
"Yeah, but it was an ice cream social as well. It was awesome, my friend passed out from too much rum raisin."
Idea can also be applied to almost anything that is an unusual place for a concert, the possibilities are endless, which is why it has probably been done in some form or another before.
Another idea: A concert venue based off of a retired large ferry boat in MA, half concert half whale watch.