none of the western languages have multiple tonal states so the skill is rare around here. it's likely it needs no special genetic disposition any more than the ability to speak does, so if I ever have kids they'll be subjected to extensive musical stimulation just to see how it goes.
of synasthesia I've absolutely no clue, but it sounds more like a genetic brain "malfunction" or some more exotic junction of brain functionality to me. probably can't be taught or learned.

