This is purely about the definition of intelligence. I read that if a class of school children (or 6th formers/college) who know each other well are asked to "rank the class in order of intelligence" their results will correlate with an IQ test. I don't know for sure whether this is credible, but it sounds right.

While musical ability may be impressive, I don't think that a musical expert who couldn't spell or do basic maths would be described as "intelligent" by most people.

I'm not intending to comment on the value of artistic abilities. But I think that calling them "intelligence" when most people don't intend this as a meaning of the word, is something done by people with low IQ scores.