YA supernatural thriller where students finish the unfinished great works of dead artists

I only have vague recollections.
I think the cover was mustard yellow with a girl in a white nightgown on it. The parents thought their children were being sent to a boarding school but instead they were used to channel the spirits of dead artist, musicians, ets. One girl finished Shubert's unfinished symphony. This would have been in the mid 70's-80's.

Is this Down a dark hall by Lois Duncan?

Thank you!! I just read the kindle sample and that's it. I think my oldest son will enjoy reading it.

Glad to have helped! I hope your son likes it - if so, Lois Duncan wrote a lot more thrillers for teens. I read a lot of them when I was younger.

I'll have to check those out as well.