Here are my thoughts on the matter.
"IQ" persay, is simply a number, it's potential, not how good you are at anything. Having a higher IQ means you have a bigger battery in your head and that things come more easily to you. Just becaue you have a high IQ doesn't mean you do well at school. Size doesn't matter, it's what you do with it.
It doesn't mean you wil be naturally more able to get farther than someone else with a lesser IQ, it simply means you will get there faster.
Afool4u, I completely agree with you on the singing part. I think that you can train someone to be a better singer, but they will never be an amazing opera singer like someone born with a good voice.