FORT WORTH — The Chamber Music Society of Fort Worth ended its season Saturday afternoon with a stellar program of three major works.The auditorium at the Modern Art Museum was as crowded as it has been since Gary Levinson took over as artistic director in the fall. This is a dramatic change, and board President John Forrester took great pleasure in announcing that Levinson’s contract has been extended for three years. “And he accepted,” Forrester added with obvious relief. Levinson, a superb violinist and senior associate concertmaster of the Dallas Symphony, took part in this concert: something he has rarely done in the past. The audience was pleased to hear him and he turned in a magnificent performance. It was a huge program, with three gigantic works, all of which required mind-boggling technical mastery and, when played together like this, superhuman endurance. Levinson and pianist Andrius Zlabys opened with Gabriel Fauré’s Violin Sonata, Opus 13. Next, Zlabys joined with cellist Anthony Ross for Sergei Rachmaninoff’s nearly impossible Cello Sonata, Opus 19. After a brief intermission, all three joined forces for the biggest and most challenging piece — Maurice Ravel’s Piano Trio.Zlabys had the biggest mountain to climb. All three are transcendentally difficult for the piano, and he alone played the entire program. He was not as sharp playing the very difficult Ravel. It may have been because he was exhausted by the other two works. Another factor could have been that the dynamic levels in the Rachmaninoff were too loud almost from the start, which can affect stamina. All told, he certainly had every right to be tired at the end, but he still did a terrific job.All three performances were magnificent. The style of each composer was perfectly realized, intonation was right on, technique was clean, and balance was good. With artists of this stature, you expect fine performances, but this was something special. It may have been the sense of occasion that inspired the players, or maybe all three were just having a great day. Whatever the reason, the spontaneous standing ovation at the end showed that the audience was thrilled. It was a far cry from the usual dutiful ovations.