For its final concert each season, the Eastern Connecticut Symphony Orchestra fills the stage at the Garde Arts Center to the bursting point. This spring performance has a lot of moving parts, as the 80-voice ECSO Chorus joins the 80-plus musicians to challenge the spatial boundaries of the Garde, and this Saturday, there's even more musical chairs than usual.

This year, ECSO Music Director Toshi Shimada will step aside on the podium for ECSO Choral Director Mark Singleton to take the baton with the ECSO for the first time to lead the forces in a pair of contrasting 20th-century works, Vaughn Williams' warm and affectionate Serenade to Music and Stravinsky's unique Symphony of Psalms.

The Stravinsky cantata-as-symphony is major artistic step for the chorus, a work steeped in the Classical traditions and structures, yet built of novel tonalities that are almost always new territory for choristers. The Symphony of Psalms is a technical mountain to scale, and its programming alone is a kudo to Singleton and his singers.

The concert opens with Shimada leading the orchestra in Mozart's three-movement Divertimento in D Major for Strings, featuring the violin and viola sections that Stravinsky omitted from the Symphony of Pslams. And the concert concludes with Stravinsky's Rite of Spring, that earth-shaking ballet suite made famous by the near-riots that disrupted its 1913 debut in Paris and by its central role in Disney's "Fantasia," as the soundtrack for dinosaur-killing cataclysms.

It's a wide-ranging, unusual and potentially thrilling program.

- MILTON MOORE

The Eastern Connecticut Symphony Orchestra and Chorus, 8 p.m. Saturday, Garde Arts Center, 325 State St., New London; $32-$62, with student discounts and $12 rush tickets the night of concert for students and active military personnel; (860) 443-2876, gardearts.org.