Following my philosophy of "Why Not Both?" I was unable to find a reason to not pursue my interest in musical composition. So, in addition to my commercial graphics major, I took some composition classes, after taking all the music theory and aural classes required for it, of course. Those few classes really gave me an appreciation for the work music majors have to put in.
I can compose at home, sell and license my works, and accept contracts that will not interfere or conflict with my work in design. I believe everyone should be able to work in the field that they enjoy doing, especially in creative fields. It's passion for what you do that really makes good, quality creations and achievements. I enjoy composing just as much as I enjoy graphic design, so why not both?