Well, I do know first hand that any type of music, listened to AND studied will increase your intelligence, but that also depends on the word itself. Listening to classical music is wonderful, but studying the composers every move and thought, seeing it on paper, having it explained to you and understanding why he/she choose to compose a particular piece, and finally playing the notes the way they were intended to be played.......I definitely believe that will give your intelligence a freakin' MEGA BOOST!!!!
Heres the thing about the classics for me. When I was in college, I got a chance to play oboe, which is pretty hard to do(my band director "commanded me" to learn, LOL! ) which meant I was able to play MORE of the classical, asside from parts written in for the saxophone. So I did it, and it worked, and I recorded alot of stuff when we went on tour. Now, out of all the music we played, the best part for me is hearing the same music in a movie, or a commerclia ect...-it gives me goosebumps everytime! My mind reverts back to the hours of work and practice, doubt and confidence,the music theory, history, and background of the piece and the composer, great times and not-so-great times spent working that music out, and I say to myself....
(this is gonna sound stupid, I know we are talking about intelligence here!)
"HEY, we played that Carmina Burana, or that Sheherezade, ect. It was awesome!"
or
"OMG! THAT'S (insert composition here) playing on (insert media here)....Whaaaaaatttt!!!?"
...your heart instantly flutters with rememberance and joy, and you feel a connection to every memory, moment, thought, people,places or things associated with what you heard, because you worked on the same piece just as hard (or less) than they did, and you brought it together for others to hear as a magnificent, finished product! It triggers the memory, music does. Therefore, it increaces your intelect, because you want to share information about that experience with others that might not know what the hell you are talking about!!!!
Goosebumps!!!