“Yale’s music major does not have a performance concentration.”
Correct. Which is why I didn’t ask the OP if he was planning to major in cello performance. I was asking if he intended to major in music and if cello performance was his primary INTEREST.
Admissions officers do not, typically, have the time to review every piece of supplemental information sent to them by enthusiastic applicants. If the OP is NOT planning to major in music then his proficiency as a cellist is significantly less important. Stating his commitment to cello and listing his accomplishments is all the admissions officer needs to know to make an informed decision (in conjunction with the rest of his file, of course).