East Lyme — Monday officially is Halloween, but Sunday afternoon is just as stuffed with costume processions, trick-or-treating, and Halloween music.

Niantic hosts its annual Halloween Parade, with participants stepping off at 2 p.m. from the Hole-in-the-Wall Beach and traveling down Main Street; a costume contest follows at St. John's Green. Before all that, though, there will be trick-or-treating at downtown shops starting at 1 p.m. The event is sponsored by the East Lyme Parks & Recreation Department.

At the Stephen Main House in North Stonington, Elena Zamolodchikova and Aymeric Dupré la Tour will play the harpsichord for "Ghosts, Gnomes, Gypsies: A Halloween Concert" at 4 and 6:30 p.m. It's $20, and reservations are required; call (860) 599-3608.

At the Westerly Armory, the Westminster Youth String Ensemble performs its own Halloween Concert at 1 p.m. Big Nazo Puppet Creatures will be part of the fun, along with kids' mask-making and a costume parade. Admission is free, but people are asked to bring a canned good for the Pawcatuck Neighborhood Center.