Mr. Nowack said: "Question for OP are you also looking for musicals with absolutely no dialogue?
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I was just reading the Cats revival forum and hearing the whole no plot and only dancing and songs claim got me curious about other musicals with a lot of songs.
THE MOST HAPPY FELLA while not at all a show with little to no dialogue has often been described as a show with a lot of music, not quite what you were asking for but along the lines.