The members of Slavic Soul Party! are not Slavs - they bear surnames such as Carlson and Caswell, Toriyama and Noriega. They have deep roots in New York's downtown scene, where jazz and ethnic music have commingled for years. Their rhythmic and improvising chops are well-developed, which is a requirement when playing riotous Balkan music in an all-acoustic lineup of horns, drums and accordion.

Clad in jeans and matching black T-shirts, the band launched a CD-release tour at International House on Wednesday night. Chairs were cleared to allow for dancing, but the adoring crowd hardly needed encouragement.

Playing a dirge, the group convened at the rear of the hall, then took the stage to play upbeat songs from the new album Teknochek Collision, named for a body shop near the Brooklyn-Queens Expressway.

Marked by catchy melodies and mercurial tempos, the band's music is inherently populist but often metrically complex, in true Balkan style. As the driving beat of "Vranje" gave way to the brisk, irregular time of "9 at the River," dancing skills were put to the test. Some in the crowd flailed, but one group of middle-aged patrons suddenly formed a line, moving hips and feet with tightly coordinated expertise.

Matt Moran, the group's leader and main composer, wielded a propulsive bass drum. Take Toriyama played snare. They were joined by two trumpets, two tenor horns, a saxophone/clarinet and tuba. Peter Stan, the one member of Balkan descent, played accordion.

The band took to the floor for the rollicking "Opa Cupa" (pronounced "tsupa"), interpolated with two note-perfect choruses of Johnny Cash's "Ring of Fire." Soon the crowd formed a circle and enveloped the musicians in a swirl of movement. The audience/artist boundary all but disappeared. But the show ended as it began, with a reprise of the solemn dirge, then a retreat to the wings.