He sucks at singing

So my boyfriend that I've known for years and been with for one year. His dream in life is to rap/sing and I always supported him, I love it when people are very passionate about their dreams. However..he is so bad. I mean I don't want to be rude and say something that would offend him and I tried mentioning classes that can improve him just like I love painting and I took art classes when I was younger till now, but he's really convinced that he doesn't need them and that he's really good and has come a long way. I don't want to hurt his feelings but I feel guilty lying to him also. He shows me his recordings all the time and even in sound cloud and is just so bad. I sometimes need to pretend and say yeah it's good but in reality I tune it out by thinking of something else. Help me please!! He honestly thinks he sounds like Chris Brown whenever he pulls a high pitch and it's so painful to hear.