The seriousness of their faces while they bang away at your instruments!
Someone ought to give you a grant.

It reminds of a scene in Kenneth Grahame's (the author of "The Wind in the Willows") "The Golden Age" or possibly "Dream Days" when the child narrator ends up in the rooms of a university student where there's a piano and the latter asks him if he wants to "have a strum". That was one of my favorite activities as a child. I remember it well.