I was the monster. The way it worked is that the monster would go into a cafe or restaurant, unexpected and scare people. The other band members would already be there, including two Japanese school girls whose job is to scream and run around. The musicians in the band would start a song to the monster. "Monster, we know you're hungry, but you can't eat these people. These are important people." The song describes each person in the restaurant, making up details about them. From there, it becomes a full musical. Each person gets their own song building on the made up details we assigned them. The monster sings his own song. There is an antagonistic who gets eaten.
And in the dream this was an established form of entertainment in Japan. It had a three syllable name with a k and an h and a j but I don't remember the name. We were the first folks to bring this art form to the states.