Saturday evening was the 60th anniversary of the first-ever St. Paul Chamber Orchestra concert, and champagne and treats were available in the Ordway atrium afterward.

Inside the hall it was business as usual — a U.S. premiere, two works by lesser-known composers, and a podium debut by a fast-rising young conductor.

The premiere was "Dark with Excessive Bright," a new concerto by the American composer Missy Mazzoli.

The title comes from Milton's epic poem "Paradise Lost" and pictures God in heaven, mysteriously cloaked and "throned inaccessible."

The unusual thing about the piece is not so much the title as the fact that it's for double bass — a bedrock of the symphony orchestra, but an instrument that barely gets a look-in when it comes to concerto repertoire.

Over a 15-minute span, "Dark with Excessive Bright" explored the bass' inner voice in music of eerie resonance.

Disorienting downward glissandos summoned an ambience in which traditional coordinates blurred and a netherworld of shifting mists and shadows was established.

Amid the swish of textures — the concerto is written for string accompaniment only — soloist Zachary Cohen hunched over his leviathan of an instrument, reaching low to find the highest notes on the fingerboard and digging primeval utterances from its inner recesses.

The effect was riveting, as if a long-suppressed voice was finally being liberated, expressing truths not normally encountered.

Cohen is principal bass of the SPCO, and his intensely committed performance stirred the audience, who gave him a prolonged ovation at the work's conclusion.

The rest of the program leaned more toward the conventional, though there was room for a rarity, the Concerto for String Orchestra by the 20th-century Polish composer Grazyna Bacewicz.

A clutch of CD issues has recently brought Bacewicz's work out of semi-obscurity, and her concerto cut a bristlingly energetic figure in the German conductor Ruth Reinhardt's incisive interpretation.

Earlier, Arthur Honegger's Pastorale d'Été had opened the concert, making quite a different impression. Amid its balmy, lapping contours, SPCO's principal horn James Ferree dropped in a number of deliciously mellow solos.

Schubert's Fifth Symphony ended the evening. This is the type of work the SPCO usually plays conductorless, and it was odd for once to see it directed from the podium.

The results were interestingly mixed. More bite and aggressive unanimity were evident in the bounding Menuetto than in a more collaborative, conductor-free interpretation. The movement gained in trenchancy as a consequence, sounding a little like a draft plan for a Bruckner Scherzo.

But in the bustling outer movements there was arguably a little too much corporate drive in evidence, and though articulation was light, some charm evaporated from the music.

That was true also in the sweet Andante, which sacrificed a little of the music's dreaminess to a more businesslike agenda.

But Reinhardt is undoubtedly a conductor with ideas and presence, and hers was an auspicious SPCO debut.

Terry Blain is a freelance classical music critic for the Star Tribune. Reach him at artsblain@gmail.com.