Rethinking my psychology seminar project

I originally planned to do my project on intelligence differences between musicians and non-musicians..but I thought that was too fague and we already know that musicians have a bigger IQ then other people.
I decided to do my study on..well here is my hypothesis: More persistent musicans have higher IQ's then less persistent musicians.
So instead of looking at people who do and don't play music..we can look at people that both play but some musicians may be at reading, making the right sounds and putting a lot of musicianship into the music. Think of great musicans like Charlie Parker and Gene Krupa..just by listening to how they play, you must believe that they were geniuses.
I was think of taking 25 good musicians and 25 ok musicians and give them somekind of IQ test and playing ability test..not sure what kind yet..got any tips on that? There are probably factors involved? (maybe being lazy, not wanting to practice or wanting to be the best...other than a ok musician's IQ.)
So what you guys think? Good study idea? If you have any tips or ideas and places where I can get reseacher on that narrow topic PLEASE let me know!
Thank you!

How would you decipher the difference between "ok" musicians and "great" musicians? Will you use their fame as guidance and find out through concrete records which were considered greater? I think you would need to careful here because personal preference and perspective could cloud judgment upon who is considered "ok" and "great".

Another thing, would you be able single out the variable of motivation in the musicians? Meaning would an "ok" musician who had a higher motivation to seek success be categorized in the "ok" or "great" based upon their fame?

I think it would be a good study but I think you would need to carefully go about it to decide who is considered "ok" and "great" and make sure extraneous variables are under control to get to the root of your study.