SALEM — A cacophony of sound drifts out of Salem's Old Town Hall and over the steamy summer air.
Shortly before 8 p.m., instrumentalists in the second-floor meeting hall are tuning up, while vocalists and visitors chat together before the Paul Madore Chorale SummerSing, an all-comers' evening of classical music that doubles as a fundraiser for the Salem-based group.
But when guest conductor David Callahan lifts his baton, order begins to take shape, and the musicians embrace Mozart's "Requiem" as one cohesive orchestra.
For three decades, SummerSing has drawn music lovers who want to play classical pieces as part of an orchestral ensemble or sing as part of a chorus. Adults pay $8 and seniors and students $6. Some people just come to listen.
Despite the formality of the music, the weekly singalong takes a surprisingly casual approach.
"We never know how many singers we're going to have, and that's the fun of it," said Mary Pelletier, co-founder of SummerSing.
Most of the 100 or so participants wear summer attire, shorts and T-shirts. Fans placed around the room do their best to cool a 180-year-old upstairs space without air conditioning. The heat doesn't dampen the fun or the energy.
The group spends the first 45 minutes or so rehearsing certain sections, then takes a brief break before diving into a work from start to finish.
"We start and everything becomes quiet and businesslike," Pelletier said. "We go through the whole thing uninterrupted, and it goes and it's magical."
Pelletier and Trudy Hill, the other SummerSing co-founder, met as members of Madore's chorale. Years ago, they atten-ded a similar singalong in Boston and decided to create their own for Salem and the North Shore. Hill and Pelletier decided to broaden the idea by inviting instrumentalists.