Sports movies, Christian movies, Tween movies, Women's Pictures, Edwardian Movies, Midwesterns, &c. Most were shot down as stupid, unattractive and inadvisable. One that didn't get the official OK and yet sprang up anyway was "Dancicals."
In musicals (dancicals' aging sibling), singing and musical performance are interwoven into the plot. In backstage musicals, Dick Powell might be telling an audience about a new song he's written, which soon evolves into some insane Busby Berkeley fever dream that would be impossible to stage except in outer space.
In other musicals, two sane, grown-ass men might seamlessly slip from dialog into snapping, then singing, dancing and jumping off walls, grabbing mannequins and other tomfoolery that leaves some viewers scratching their heads wandering, "What the heck was that?" The age old question of whether or not musical numbers are actually occurring within the diegesis can't really be answered. You just have to not think about it.
With the onslaught of rock 'n' roll, musicals slipped in popularity in the 1960s. Interestingly, with the death of rock 'n' roll musicals have grown more popular again, with modern examples like Velvet Goldmine, Hedwig & the Angry Inch, Moulin Rouge!, Chicago, Sweeney Todd, &c.