The tuition for classes that apply to your minor is the same as for classes that apply to your major. It's a matter of how you calculate the credits for your graduation. So a minor costs you more because you are taking more classes than are required for your major. That said, I think they are usually worth it because they show more of your interests and personality than just a B. A. on its own.
I got a minor at the last minute because my interests were changing in those last couple of years of school. My major was Behavioral Science. Toward the end of that course of study, I realized that I enjoyed the writing part of the experiments most, so I got a part-time job with the school newspaper. It was awesome, so I decided at the last minute to earn a minor in Journalism and Public Communications. I then chose not to continue on to graduate school in Psychology, and I have made a great living as a writer ever since. The minor came in handy because a) I learned a lot about the craft of writing in just a few classes, b) I won a writing award in one of the classes and that helped me to get a job with the city newspaper after graduation, and c) it makes my resume look more well-rounded.
In your situation, I would recommend working back from the outcome you desire. You said you want to get the minor in order to do music performance? You can learn that without paying for college-level classes. Are you 21? There are usually experienced local musicians who play gigs around town and some of them like to share their knowledge for free, while others will teach you for a small fee. If you go to open mics, you can practice your solo act there. If you think you may want to teach music someday, then a formal credential may be more useful. If you think you may want to work music into your career somehow, then the minor would be worth it. You could end up writing for Rolling Stone magazine!
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