A kind of dialectic materialized at Sanders Theatre with the Mercury Orchestra in its concert last night of Wagner, Bartók, and Brahms. My first encounter with this huge pool of amateur musicians surprised me over and over again via its pronounced depth of talent and technical accomplishment. In fact, so much so, I am astonished that these dedicated musicians — some 100 — are amateurs.  Its conductor, Channing Yu, though, steered a good deal of this musical and orchestral potential to unsatisfying directions. Edgy, vaguely shaped profiling produced sameness throughout the otherwise refreshing Cambridge summer evening.

Besides marveling over this community orchestra’s musicians, there was little else to take away from the five-year old Mercury. Perhaps a future hearing might prove different. Surely, these advanced musicians, as they appeared to me, have the capability of creating far more varied expressions; this would especially be true in the Brahms’s Symphony No. 1 in C minor, op. 68. For instance, the memorable theme of the last movement, which is scored for the strings’ richness, was clipped to the point of deferring its poetics to the past, its original humanness surrendered to trendy automation.

In one of the rare moments of orchestral brilliance, dynamic balance, clear concept, and appropriate expression surfaced: Bartók’s The Miraculous Mandarin (complete version) came fully and terrifyingly alive during the diabolical embrace between the mandarin and the girl. Disappointingly, such astounding achievement was only short-lived. Under Yu’s baton, Mercury was unable to sustain that hallucinatory state specific to the Hungarian composer and his early opus. The potential was there, I would again point out.

Wagner’s Overture to Tannhäuser went fairly well for the concert opener. Oddly enough, it was preceded by a short vocal introduction from the Seraphim Singers in Bach’s “Du heilige Brunst, süsser Trost” from Der Geist hilft unser Schwachheit auf. Whatever connections the programmers had in mind eluded me as the adjacency of Bach and Wagner did not feel at all right. Wagner and Mercury dwarfed the small ensemble, which sang from the balcony, further minimalizing its presence.

We arrived early for the concert and remained in our seats during the intermission, some 40 minutes in total, during which the timpanist practiced and thumped away. One result: the Brahms opening that suddenly presents itself with urgent, punctuating tympani was lessened. I realized then I had become “tympanied out.”

David Patterson, professor of Music and former chairman of the Performing Arts Department at UMass Boston, was recipient of a Fulbright Scholar Award and the Chancellor’s Distinction in  Teaching Award. He studied with Nadia Boulanger and Olivier Messiaen in Paris and holds a PhD from Harvard University.