Complexity in music is a very ambiguous "measure". Look at e.g. Brubeck's "Take five", which many consider "complex" because of the unusual time signature; but it's actually a pretty simple piece. On the other hand, look at "minimal music" such as e.g. Steve Reich's "Music for 18 musicians"; it's based on just a few simple rules, but the resul is far from simple. When even the topic of a study is ambiguous, what can we expect from the results.