What are my chances of acceptance to Columbia University and Northwestern?

For NU you’re maybe competitive if you applied to Bienen given your musical talent, to all the other schools at NU I’d say your chances aren’t impossible but low. I don’t know about Columbia so I can’t judge but generally they have an even lower acceptance rate. Your GPA and test scores are a little low for RD, but a good essay might balance your profile out. Are you a Junior or Senior? As puzzled123 said, if you’re a junior try to improve test scores and GPA and consider ED for your favorite school to greatly improve your chances; If you’re a Senior, your stats are ok but your probably only competitive if you applied to a music school and showed a lot of interest in your essays.