In reply to Margaret.

@Margaret: Most colleges will set out quite clearly what information they expect to see in applicants' portfolios, so start by looking at the guidelines posted by the admissions department at the college. If you find that the information is not clear, don't be afraid to contact the admissions secretary or officer at the college: they are there to help answer questions like that, and will be pleased to help you. If you really can't get specific advice from the institution to which your son is applying, then good advice would be to pick no more than half a dozen pieces that are representative of his work, if possible showing contrasting styles, techniques and instrumentation, and submit that. If you have recordings or other performances of any of the pieces hosted on YouTube or Soundcloud, then include those links as well. Good luck!