How do you teach Hanyu Pinyin if your child is tone deaf

My son is in P1 now and is having issues handling hanyu pinyin, especially with the 4 tones. He is not totally tone deaf, but he finds it difficult to differentiate certain sounds like "ban" vs "bai". I also notice that when it comes to songs, he hardly enjoys singing and even if he does sing, its pretty monotonous. How do you think I can improve his hearing?
 

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