The Academy of Music on Main Street is one of the oldest operating theatres in New England — a red-brick Victorian building from 1891 that is owned by the city of Northampton and still hosts a mixed programme of films, concerts, and live performance. The interior has been carefully maintained: a main hall with a horseshoe balcony, original plasterwork, and good acoustics for a room its size.
The Academy has the distinction of being one of the longest-continuously-operating municipal theatres in the United States. Check the programme online — it tends to book independent and art-house films alongside touring musicians and occasional theatre. Tickets are cheap.