Making instruments in 3d with found objects. If they can make a sound even better!
I like to turn this into a guessing game where the groups go off to make a picture of a musical instrument.
Ideally in a frame. So we can see what is picture and what is not.
When time is up we come over to each picture in turn, and try to guess what the picture is of... and if we need a clue the artists can play or add sound effects to the picture!