You need proof of class hours when applying, and it is best to have a Test-daf score before entering school. Some schools even need it when you apply, and even if you don't need it, you must make it up within one year after admission.
If your major is ok, the professor says it is ok, you can apply for the first semester of undergraduate course.
If you have no problem with German, a friend in Germany can help you contact a professor. You can apply for it yourself or find an intermediary.
There are many language schools in Germany with different prices, but if you start from scratch, you need at least 10000 euros in the first year, including living expenses. So I suggest you have a language foundation before you go. You can learn a complete German class in advance, and it will be much better to master a certain language. I suggest you go to the German National Conservatory of Music to see the application conditions and specific procedures.