My son is not big into music at all. He's never really enjoyed singing or being sung to. When he was a newborn DH's grandfather who sings opera tried to sing him a song to calm him down. He told us all the grandkids loved it, but DS wailed and got more hysterical because of it. MIL also tried singing her own special little song that calmed all the little ones down, and it never worked.
When he was 3 or 4 I'd try to sing with him and he'd always tell me to stop it. I kinda felt bad! I was in a musicals and thought my singing was okay.
I've seen him sing a few times in church and school programs and it makes me happy, although he never seems to know the words. I think he usually tunes out during music lessons.
I don't think there is any way he ever would have sat through a Kindermusik class.
Good for you for trying, though.