balancing other interests (e.g. music) vs. interest in math

Your kiddo will lead the way. Ours wanted to play an instrument after listening to kids classical played like crazy before age 10. Then math became the thing. Now math is still front and center but not competitive math ( into another stem thing >10 hours a week). I just followed his/her lead. If they have passion about something they can come back and revisit. Kids who go really far in a field say nationally ranked in math might tire of it and go into science or really anything. They run out of time as they get older and things become more intense or they ( or the parents) push too hard and they get stressed. Best to let them lead the way.