My ds8 has never been interested in sports or music.
In our town, music is introduced through the schools in 5th grade. DS hadn't been very interested before that, but he was allowed to do band with the 5th graders when he was in 4th grade to see if he would be able to build friendship 'in case' a skip was going to be offered. He loved his brass instrument. I think that if the school offers music, that it's a great idea to take them up on it, if the child has any interest.
I think that at age 8 it's fine not to have a 'sport' as long as the child is playing actively. Kick ball, wall ball, king of the hill and tag were school yard games that my son grew to love between ages of 9 and 11. At age 8, most of DS's agemates were involved in 'little hitters' and 'little kickers' etc. It was hard to line up a play date that didn't conflict with the sports schedule. When asked which sport DS played, I'd say: 'Oh, DS retired from professional sports.'
HTH,
Grinity
