MUSIC REVIEW : String Quartet Opens Seal Beach Festival With Vigor : The newly formed group performs with bracing, muscular presence, despite showing some signs of tentative ensemble.

The newly formed Festival String Quartet launched the 17th annual Seal Beach Chamber Music Festival with vigor Tuesday at the McGaugh School auditorium, and the festival may have obligingly returned the favor.

The quartet was brought in--at the 11th hour, one suspects--to take the place of the originally announced Southwest Chamber Music Society, which, according to festival founder Alan Parker, had to withdraw because of a recording commitment.

The group includes three members of the Pacific Symphony--violinists Rachel Robinson and Robert Schumitzky and cellist Andrew Honea--and violist Craig Gibson, who has played with the Pacific for three years as a substitute. Each also is a member of other Southland orchestras.

In their attractive program of Vivaldi, lesser-known Mozart and Dvorak, the players showed signs of tentative ensemble and lack of direction and finesse, all attributable to their brief life span together.

But they also played with bracing, muscular presence and demonstrated strong, intelligent response to the music and to each other. Gibson perhaps served as the suave center of the vortex.

Vivaldi’s “Sonata al Santo Sepolcro,” which opened the program, not surprisingly showed the group unsettled and nervous.

Moreover, the brevity of the two-movement work apparently befuddled the audience, which gave the players dead silence at the end. Only when the musicians appeared ready to start the next piece did the audience respond.

Then, as if to make up for the gaffe, people clapped after every movement of the two works that followed. The peak of their enthusiasm occurred when a woman said, “Oh, wow!” after the Lento of Dvorak’s “American” Quartet.

Misjudgments of accent and overdrive occurred in the Dvorak work, but, on balance, the players’ spirited commitment to the piece, plus Robinson’s tracing sweet humor in the closing theme, prevailed.

The ensemble found little sweetness and grace in Mozart’s D-minor Quartet, K. 173, written when the composer was 17. But the players did pursue him earnestly in his uncharacteristically boxy and inconsistent Sturm und Drang mood.

The free festival will continue with other ensembles and soloists over the next five Tuesdays, through Aug. 13.