The Yale School of Music takes only graduate students. There are undergraduate degrees awarded in the department of music, but those degrees are focused on music theory, not performance. The admissions procedure is the same as for any other subject in Yale College (the undergraduate division of Yale).

Any college or university you apply to will look at your test scores and GPA. Because you first have to get into the school itself and then usually into your major or sometimes pre-major program. And they want the best students no matter the major. Even if your major is music you take more than just music classes. Each school has certain classes (English, math, humanities, etc) that everyone must take to graduate. And yes can can transfer and change major no matter what year you’re in. And I’m not 100% sure about Yale music school but it’s most likely will still be as hard to get into as you know getting into Yale as a English major. Check the website to see what you need to apply. Some music programs require auditions to get in.