People may be slightly unsure as the admissions office does not review msic supplements. The music department itself is very kind and reviews the supplements for them. Here is the link to how submit a music supplement: MIT Music Program: Prospective Students - Admission Supplements
note how it says:
At the moment we are only able to evaluate supplements in the fields of classical, jazz, and world music performance, as well as classical and jazz composition.
I think if you know enough about music to submit a supplement you should be able to make the call of what your music talents fit into.