Christopher Zimmerman conducts the Fairfax Symphony Orchestra at George Mason University’s Center for the Arts Concert Hall. (F Barry Wheeler)

The overture to Rossini’s opera “La Gazza Ladra” and Tchaikovsky’s Symphony No. 6 in B Minor (“Pathetique”) exist in opposite universes — the first, a place where confidence and bumptious good humor rules; the other, a cauldron of dark passions and fierce exaltation. What they share, however, is an imperative for urgent momentum. And conductor Christopher Zimmerman and his Fairfax Symphony Orchestra do momentum exceedingly well.

Their program at George Mason University’s Center for the Arts on Saturday opened with the Rossini and ended with the Tchaikovsky, revealing a string section that never let velocity blur its crisp ensemble, a wind section that handled the spotlight eagerly and a percussion section that had a field day in both pieces. Sure, there were moments when the dialogue between strings and woodwinds could have been smoother and others where the cellos could have had more heft. But the spirit of the Rossini was delightful and Zimmerman drove a clearly mapped course through the thicket of the symphony that focused on its architecture and reveled in its contrasts.

Between these two confidently assured performances was a rather tentative reading of Tchaikovsky’s Piano Concerto No. 1, with James Dick as soloist. When I last heard Dick, it was his attention to detail that was most impressive. Here, it was detail he seemed to struggle with, and it was clear that he and Zimmerman had not come to a common understanding about the music. Zimmerman wanted to move on while Dick was immersing himself in shaping subtle rubatos, and there were times, particularly in the first movement, when neither seemed sure of the other’s whereabouts.