[steamer25]

I was replying to another sub-thread here and had another thought:

It might be easier for your son to express what he's learning if you can catch him while he's got e.g., a piano or guitar at hand. Humans have a hard time generating compound musical waveforms using just their bodies/vocal-folds (though it can be done to a limited extent as in Mongolian throat singing). Having him play the sounds as he explains them will probably also help cement the concepts in his own understanding ;) .