The Palace of Fine Arts (Av. Máximo Gómez, www.bellasartes.gov.do [1], tel. 809/682-1325) is an impressively large theater that holds special performance events including the symphony, dance productions, and exhibits. Events are quite sporadic, so look in the local papers, consult with the concierge at your hotel, or call for a schedule.
Links:
[1] http://www.bellasartes.gov.do