Just about all the Gilbert and Sullivans (earliest musicals?)
When I was a student, I was at a uni that had three theatrical societies, namely:
Theatre Group - all the non-musical stuff
Music Theatre - Joseph, Guys & Dolls, Hair etc
Light Opera Society - Gilbert & Sullivan
I don't know if that distinction between G&S and Other Musicals still exists though.
There's a lot of snobbery about the theatre. I was only ever in TG, but I only avoided the others because I could neither sing nor dance. But some people avoided them because they didn't consider musicals as real theatre. They were wrong. I never considered myself a fan of musicals until one day I sat down and thought... well, yes, I do like this one... and I do like that one... and that one too... and then I realised that I actually like lots of musicals. Yeah, some musicals are rubbish, but the best ones are really very good.
I also tried to subvert TG by putting on Brecht, who did like a song or two in his plays.
d.