A modern update to the opera (or, more accurately, the operetta), with the only significant change being the use of contemporary and popular music instead of classical. Musicals are generally derided by the same people who dislike opera, and for generally the same reason: it's implausable that a group of people would suddenly break into four-part harmony at an emotional moment without having to ask each other what the lyrics are.
But as with most other plays and movies, you have to suspend your disbelief a little bit. These people presume that the songs are written to fill out the plot, when usually the opposite is true: the plot is there to provide an excuse for the music. It's a concert with a story to help make it interesting.