Hello positivesteem, working with sound and different instruments is a great way to express yourself and receive positive impact of sound. One great tool is drumming, just get your son a simple jembe drum, could be a lighter one made of carbon or real woodden made which would create more sound impact. Kids react good on drums and vibrations produced goes through all body creating nice stimulating effect. Also sound is activating ether, a subtle vibratory energy within the mind body space which promotes health and well being. The other instrument which works well is Australian didgeridoo. It takes some effort to learn how to play it but the rewards follow. It could be home made out of carton or water pipe tube, a bamboo or eucalyptus tree made as the original ones. Start with home made and progress. Didgerodoo has strong low vibrations and they again vibrate the whole body for good effect. Last I would suggest rhythmical instruments, shakers. They help with fidgeting momentum, lowering anxiety and bringing joy. Hope this helps a little...