If you cannot fit a science into your schedule, your guidance counselor can explain that to the colleges.
If you like science and want to continue in it, a summer course is absolutely fine, as would an online science class (yes they have labs). Summer science can be pretty intensive. Make sure there isn’t something better for you to do during those months 
If music is an interest, do NOT drop music theory. I know of someone who was admitted to Harvard who dropped way back in math in order to take music theory, and Harvard seemed to appreciate the dedication.
If you are accomplished in music, the missing science may not even matter.
Please do what interests you and what provides a balanced life. If you want to, you can explain the limitations of your school scheduling as well as what “passions” dictate your choices at some point, as can your GC.
In the end (repeating this once more) you want a school that fits you, rather than twisting things to fit a school. The irony is that, by exploring authentic interests and looking after your well-being, you may actually have a better shot at selective schools than if you try to fit a template.