The Orpheus Chamber Orchestra, a unique conductor-less assemblage formed in 1972, continues to impress and frustrate. Drawing its members from the cream of the New York freelance pool, it handles the most complex modern works, as well as earlier repertoire, with uncanny skill and aplomb. At Saturday evening’s appearance at George Mason University, with violin soloist Arabella Steinbacher, Orpheus again flashed its “how-do-they-do-it?” chops and again raised nagging questions about the nature of collaborative interpretation.

Make no mistake, each Orpheus musician is a virtuoso, and you will never see such attentive personal involvement from front to back in any conventional orchestra. But there will always be a limit to their efforts. A string quartet (to which Orpheus has often been compared) operates on the principle that all four members are equally responsible and invested in the musical product, and thus all four would contribute equally in rehearsal. In a quartet, all four members can see and hear each other at all times, and any of the four parts could be the leading voice which the others must follow.

But in a Haydn symphony, the second horn part will never be equal to the first violin, nor can the second hornist accurately balance his voice against all the instruments in front of and facing away from him. Despite its preternatural ensemble abilities, Orpheus has always had issues with balance, because in performance there is no ear at the front of the group making moment-to-moment adjustments (i.e., a conductor).

Such problems permeated the otherwise remarkable playing throughout the evening. The opening “Serenade for Winds” by Strauss was golden-toned and lovely, but here and there, the different embouchures of the various instruments produced notes at slightly different starting points (with a conductor indicating a beat, it’s easier for everyone to anticipate together).

Steinbacher was impressive in two short Mozart works, particularly the Rondo K. 373, where the musicmaking had freedom, purity and joy. She also presented the rarely heard “Concerto Funebre” by Karl Hartmann, which has too few ideas at too great a length, but fervent playing by all made it worthwhile.

In the concluding Haydn Symphony No. 104, the extremely fast tempos in the outer movements brought dazzling playing, somehow perfectly together, but again opacity in loud tutti passages.

— Robert Battey