Michael Hollinger’s “Opus” is as thrilling, well constructed and turbulent as any Beethoven string quartet. It plays through April 26 at the Old Globe’s temporary arena stage at James S. Copley Auditorium in Balboa Park. Playing in a string quartet, says fictional first violinist Elliot, should be “a discourse among four reasonable people.” The reality is quite different. Because it is written out, with tempo and dynamics usually indicated as well, classical music is controlled; human behavior is not. Hollinger ought to know. He trained at Oberlin College as a violist, and then switched to play writing. “Opus” presents a gripping, intriguing character study of five musicians, each sensitive and, in varying degrees, volatile. String quartets, especially younger, American quartets, are less autocratic than before; even though some still believe the first violinist is the boss. First violinist Elliot (an extraordinarily sensitive yet restrained performance by Jim Abele, who played the second husband in the Globe’s “The Pleasure of His Company”) may yearn to command, but in truth the Lazara Quartet is run democratically; a majority, preferably unanimous, decides. Having met as students at Philadelphia’s Curtis Institute of Music, the fictional quartet is named for an 18th-century string-instrument maker. As part of their community property they possess two Lazara instruments, a violin and a viola. Second violinist Alan (Jeffrey M. Bender) and cellist Carl (Corey Brill, also UCSD, MFA) are voices of reason, and yet, they express strong opinions as well, ultimately deciding who stays and who goes. In the case of violist Dorian, they agree with Elliot to oust Dorian, the violist. With his tousled hair and romantic good looks, Dorian (Mark H. Dodd) is a perfectionist and the most emotional of the quartet. The audience learns in later flashbacks that he disrupted the final session in Lazara’s complete recordings of the Beethoven string quartets. After being released from his contract, Dorian disappeared, off his mood-swing meds, his longtime, verboten affair with Elliot ended. When the play begins, the remaining three are auditioning for a new violist. A White House command performance looms, so the position needs immediate filling. They choose a young woman named Grace (excellent Katie Sigismund, a UCSD MFA graduate), who hesitates and not because she knows the quartet’s inner strife. She has an audition the following week for first chair viola in the Pittsburgh Symphony Orchestra. The others berate her, asking, “You’d trade playing in an orchestra for this?” She changes her mind. In live performance, quartet playing is most exciting for players and audience alike. One never knows when a string will break. According to Emerson Quartet cellist David Finckel (in an archived 1999 interview), the audience doesn’t pay to see perfection. “You want to be spontaneous,” Finckel said. “The concert is the place to take chances. It should be unpredictable, alive and fresh.” The same can be said for Hollinger’s play, which unfolds, in director Kyle Donnelly’s sure hands, like a piece of chamber music, rife with movement, intertwining and overlapping dialogue, solo and duet sections. Although the actors do not play their instruments, they do a believable job of miming, albeit without hand vibrato, which kills the illusion for regular concertgoers. Because the players switch places around the playing space and the placement of speakers is phonically stationary, it’s sometimes unclear who’s on first (pun intended). Lindsay Jones’ otherwise unerring sound design uses music of Bach, Beethoven, Pachelbel, Bartok and even the Beach Boys. Kate Edmunds’ scenic design is composed largely of music stands. Denitsa D. Bliznakova’s costumes are attractive, and York Kennedy’s lighting design is immaculate. The denouement, which takes place immediately after the White House performance, is thrilling, turbulent, shocking and bravely unresolved. It puts one in mind of the true and ugly breakup of the Audubon String Quartet, which resulted in a long court battle and altered many lives. Thanks to extraordinary direction and casting of magnificent actors, there are no dull movements in “Opus,” which fairly flies along in one allegro vivace act. It’s a brilliant piece of theatre, the best work yet seen in the Globe’s temporary arena space. “Opus” continues at 7 p.m. Sundays, Tuesdays and Wednesdays; 8 p.m. Thursdays through Saturdays; and 2 p.m. Saturdays and Sundays through April 26 at the Old Globe arena space, James S. Copley Auditorium, San Diego Museum of Art, Balboa Park. For tickets ($29-$59), visit www.theoldglobe.org or call (619) 23-GLOBE.