This lesson will take a couple of days, but my 6th graders are enjoying it.
Procedure: Divide the class into groups of 5 or so. Give each group a drama scenario. Example: You're in a museum. You see a "statue" move. You try telling the rest of your group but since they didn't see it, they don't believe you. The statue only moves when you're watching it.
The group decides on who plays what part.
They work out the scene by first pantomiming the scene.
Next they go back and add nonsense syllable dialogue. I call this blah blahing the scene.
The next class meeting the groups rehearse with real dialogue.
They finally improvise singing parts while someone creates an accompaniment on piano or Orff xylophone.