I agree with you. Learning Putonghua is not so difficult. Cantonese is a different story.

If one is unfortunate enough to be tone deaf it can be nearly impossible- and with that disability it's probably not worth the effort; since it wouldn't exactly be a walk in the park for perfect-pitch types haha. However, you get congenitally tone-deaf Chinese and somehow they manage to overcome- I suppose they learn where to place the tongue and so forth...receiving would be another matter and mistakes will always be made- can't always rely on context and experience. Turnoi will know- we should ask him.