Comment by calf
Yours is the first comment I strongly agree with; as a multilingual/bicultural Asian American, children don't have this supposed difficulty hearing tones.
Most of it is passively paying attention. It should not be a struggle, it's one of those the more you struggle and overintellectualize the less time you are focusing on paying attention and letting your hearing ability do its work it was evolved to do.
The other thing is this whole emphasis on accents is misdirected. Teachers do not place this excessive emphasis on accents, it is people who want to sound "authentic" which is not a very wise goal of language learning in the first place.
I do think that learning music can help a little, especially a sonically complex instrument like violin and the like.
(caveat: I'm way oversimplifying on my Saturday afternoon, but that's my tentative views on this that I would try to argue for.)
I agree on not over-intellectualizing the tones.
I've seen people struggle to pronounce a word when I explicitly tell them what tones it contains, but then pronounce it perfectly when I ask them to just imitate me.
But I disagree about accents. One of the major flaws in most foreign language education, in my opinion, is that pronunciation is not emphasized heavily enough at the beginning. Being able to pronounce the basic sounds correctly has a huge impact on how native speakers perceive your language skills, even if you're not very advanced in the language.