This activity gives the children a chance to control each other’s sounds by making different signals.
1) Choose a person to be the conductor (you could be the conductor the first time to show the children what to do).
2) Explain that when you move your arm HIGH up in the air, you want them to make a “Laa” sound with a HIGH pitch. If you put your arm down LOW, they should make a LOW-sounding “Laa”. Also, indicate the signals for starting (e.g. “thumbs-up”) and stopping (e.g. flat hand facing them).
3) Begin moving your arm up and down and making slow and quick movements.
When you have finished, other children can be the conductor, and they can control the pitch of the “Laas” (high arm=high pitch, low arm=low pitch) or the dynamics of them (high arm=loud, low arm=quiet).
Once the children are familiar with this activity, you could let the “orchestra” use instruments. You could also split them into groups of similar instruments, with the conductor controlling the pitch / dynamics of each group when he moves near them.