I would say it's an unwise decision. Back when I started school six years ago, it was pretty much a "rule" that in order to be successful, you go to college after high school. And that is true, if you want a good-paying job, but you have to be careful, because what colleges fail to emphasise is that this is a debt you will take on, and you want to make sure you can pay for it. Certain schools on the coasts are outrageous, charging 100K for a four to five year Bachelor's degree! In the midwest, I walked away owing 40K, but I have a nursing degree, and my first job will net me about 45K that first year of work.
To really look at the whole college education thing, my strongest advice is to LOOK at the job marketability of what you are planning on doing. What is the likelihood of you being able to get a job with that degree, and not only a job, but one that allows you to pay the bills, and tuck back a little bit in savings each month? My strongest desire was a piano performance degree, but if I would have done that at the university I had originally attended, I would owe close to 100K. Instead, after a year of that, I chose to do something else that I truly loved for work, nursing, which allows me to help people, and it also allows me to FINANCE the other things in life I love, such as music. Now, once I wrap up the nursing degree, I'm going to give myself a couple of months to get situated, and then start in with classes at a local community college to learn the theory and composition at a MUCH cheaper rate, and I will pay those as I go.
To be honest, the days are over when you could just get a degree in whatever you loved, and then started working using that degree and make a decent living. Certain majors are suicide in terms of success, such as a bachelors in psychology, or a bachelors in journalism, for the simple fact that the cost of the degree is so expensive, that their salaries with those jobs do not allow them to make ends meet. With the trends of the country (talking United States here), getting degrees related to technology, healthcare, or law are the most lucrative. You have to look at the job prospects, the cost of the education, and whether or not crunching the numbers allows you to come out on top.
That's not to discourage you from taking music courses while you are in college, but if I could do it all over again, I would have gone to a community college until I got accepted to nursing school. It's so much more affordable, so my advice would be to go to a community college first, and take as many courses as you can before transferring to a 4-year university. Also, SHOP around. My advice is to not go to a university because of the name. I made that mistake with K-State, because it was where everybody went, and their school spirit was awesome and their campus was gorgeous, but as of today, it's to the tune of 20K a year. So not worth it. Look into how much they charge per credit hour. The current university I go to has a flat rate on full and part time students. Full-time, regardless of how many credit hours you take, whether it be 12 or 20, is $2,800 a semester in tuition. So, you could pile on the coursework (within reason), even finish a degree faster (or take music courses without incurring any additional cost), and still make it affordable. I hope this helps, but as others have said... It's not exactly necessary to have a degree in music, unless the job you are after makes it necessary. Even then, plan, and think smart.
Those are just my thoughts. Hope this helps.