Hello~
I’m currently a sophomore at an IB school.
I received all 7/7s last year and currently.
However, I will probably receive a 6 in music this year because of music composition.
I have no plan of doing music in university and I chose it because I had to 
Will a drop in grades due to music affect my chances of getting in to my dreams schools, HYPSM?
Thank you 
Breathe. It is fine.
If you don’t get into HYSPM it won’t be because of a 6 in music composition.
And FWIW many colleges recalculate GPA using academic subjects only.
However as a bit of unsolicited advice – from other posts you seem way too focused in on getting into HYPSM. Even with perfect grades, perfect standardized testing, great ECs, amazing LORs and essays, etc. nothing can come close to assuring you a spot at one of those schools. With acceptance rates well below 10%.HYPSM as well as other top tier colleges routinely have to turn down exemplary applicants. Please stop your focus on these few hyper-competitive schools and work to develop a well crafted list that also includes match and safety schools that appear affordable and that you will be happy to attend. You need to expand your horizons and recognize that there are many wonderful schools out there where you can have a great 4 year experience and get where you want to go in life.
They won’t throw your app out because of one 6.
Avoid using the term dream school. Your goal should be to apply to a range of schools that you can afford and would be happy to attend.
The only thing to worry about in this thread is your thought that HYPSM are your dream schools. You need to think about what you actually want in a university. An abstract notion that a big name matters is going to get old within a few weeks or at most a few months of when you arrive on-campus.
I have a list of universities I would love to attend and fit my major.
I just mentioned hypsm as they are the most competitive on my list.