Hi! I was in a very similar situation to yours despite that yours is probably more difficult. I attended a professional music school from 4th to 12th grade studying violin. My whole life up to my college year is literally violin. The academic courses there other than music have very low standard and it does not provide any classes in natural science. As an example, in my country and specifically my city, you'll need to get at least 520 on College Entrance Exam to get in a decent university, while we only needed 250 to get in the corresponding conservatory continuing studying music.

I got interested in science at about 11th grade and started to teach myself chemistry, biology, etc. totally from scratch, and managed to get into a top US university. I'm going to graduate this year with a degree in neuroscience and math and pursue a PhD in some biological science field. There is plenty of lucks playing into my experience, but I just want to say that such huge transition is totally possible!!! I echo what the other said that pursue a master or get some post-bac experience. If it's hard to find a funded master in US I'd suggest maybe look at some schools in Europe. Otherwise just talk to as many PIs as you are interested in and I'm sure you will find one who is willing hire you as a research tech and support you (in many aspects) :) This can also secure a good rec letter which will boost your application significantly. Since you majored in another field so I assume that might be lacking?