Fill up bottles carefully with various levels water so they make tuned notes when blown across the top. Then yourself, or even better, with a group, play some songs. If you have may people, one per note even, you should be able to play a song quite smoothly. You can even play sustained chords for expert music reader and have larger deeper bottles for bass notes. If you have a large group in a circle, and a lot of bottles, each person could play just one note in the song as the conductor points around the circle when to play.
