Although I don't know of anything that states whether there is a direct
correlation between music appreciation and IQ level, I DO know that people
who are musically talented, or have at least been musically trained, have a
tendency to do well in other fields. It is well known that whether a person
thinks with the left-brain or the right-brain influences their perceptions
(of everything), as well as, the thought processes which influence those
perceptions. Music is mathematically based and therefore bridges the gaps
between artistic/creative and logical thinking, unlike most other artforms
which are more creatively derived. People who have musical
skills/talent/training, whatever you want to call it, are able to utilize
their creative-brains logically and their logical-brains creatively. It is
also popularly know in psychology that people who are able to utilize their
whole brain in this manner ARE smarter. Another thing to remember, IQ is
only an indication, not a true measure of intelligence.