What do orchestral musicians do in their free time? Many embrace the busman's holiday that is chamber music. Playing in a small ensemble is a tough way to make a living -- supply outstrips demand -- but with an orchestral paycheck to cover the mortgage, it is one of music's most congenial and rewarding pursuits, affording opportunities for individual expression, and for direct connection with listeners, that are largely foreclosed in an orchestral (read: industrial) setting.

Case in point: Accordo, a new five-member string assemblage comprising principal players of the St. Paul Chamber Orchestra and Minnesota Orchestra (though heavily weighted toward the former) that made an auspicious debut Sunday amid the flattering acoustics of Minneapolis' Southern Theater.

Rather than taking a single form, fixed in instrumentation and personnel, Accordo (Italian for "chord") has adopted the "chamber-music society" model, drawing duos, trios and quartets from its membership so as to embrace a more varied repertoire. Thus Sunday's inaugural concert began with violinists Steven Copes and Ruggero Allifranchini in Prokofiev's terse Sonata for Two Violins, added violist Maiya Papach and cellist Ronald Thomas for Shostakovich's searing String Quartet No. 3 and then subtracted Allifranchini for Mozart's consummate E-flat Divertimento. (Cellist Anthony Ross, the group's lone emissary from the Minnesota Orchestra, will be heard on its next program.)

Stand partners in the SPCO, Copes (armed with a bright-toned instrument by Guarneri del Gesù) and Allifranchini (who deploys a mellower Strad) are very different violinists, but play impeccably together; their gutsy, aerobic account of Prokofiev's 1932 Sonata -- accompanied by Allifranchini's mobile eyebrows and improvised, whole-body choreography -- left me wondering why it remains so little known.

Shostakovich's Third Quartet (1946) may lack the iconic status of his Eighth, but it's one of his best pieces, and Accordo's gripping performance, which sounded like the work of a much more seasoned ensemble, left nothing to be desired. From the tart jauntiness of the opening to the final lamentation (heart-rendingly played by Allifranchini), the musicians encompassed the work's huge emotional range -- its grotesquerie, its brutality, its grief. The molten beauty of Papach's viola tone was especially memorable.

Mozart's expansive Divertimento, K. 563, is the finest string trio in the repertory -- only Schoenberg's, written after a near-death experience, is comparable -- posing as an entertainment. If Sunday's performance occasionally seemed more virtuosic than stylish, it nevertheless captured the music's sensuousness and depth.

Larry Fuchsberg writes regularly about music.