Advice for someone heading to music school

All-
On one of my math newsgroups a question was posed as to what final
math course a high school student who is planning to go to music school
should take. I therefore ask you for your opinion on these questions, for
reposting to said newsgroup.

1. As a music theorist, what math do you use frequently?
2. Is there some branch of mathematics that you wish you had studied?
3. If you could advise a student to take one specific math course to
prepare her for a career in performance, what would it be, if any?
4. What do you think is the minimum math required for a career as a music
theorist?
5. Should musicians or theorists take math from the mathematics
department, or would they be better served learning the math that they
need from their music professors as they need it?

John Starrett
http://www-math.cudenver.edu/~jstarret