To lose one singer on the day of a concert is bad luck. To lose both, as Oscar Wilde might have put it, looks like carelessness.

Joking aside, that is the situation the St. Paul Chamber Orchestra found itself in around 1 p.m. Saturday.

With just seven hours until that evening's concert, both soloists for Pergolesi's Stabat Mater withdrew due to illness.

A flurry of panicky phone calls later, replacements game enough to do the Pergolesi on ridiculously short notice had been located and were busily going through the score with conductor Jonathan Cohen.

The singers in question were Scottish soprano Carine Tinney (who happened to be visiting friends in the Twin Cities) and mezzo-soprano Adriana Zabala, a regular at the Minnesota Opera.

It was a tribute to both singers' sang-froid and professionalism that if Artistic Director Kyu-Young Kim hadn't explained the situation to the audience beforehand, you never would have guessed the behind-the-scenes emergency.

Stabat Mater sets a medieval Latin poem describing the agony of Christ's mother as her son is crucified and contemplating the significance of his sacrifice.

It has eight movements in which the soloists sing together, and a natural blend between them is indispensable. Serendipitously, Tinney and Zabala had it, their voices dovetailing mellifluously in terms of size and tonal color.

Despite the skimpy rehearsal time they also had confidence aplenty in the pinging, ricochet rhythms of "Fac, ut ardeat cor meum" and the ardent "Amen" at the conclusion.

Tinney's high notes caught the ear particularly — they had a pearly, opalescent quality and a purity of timbre recalling the young Emma Kirkby.

Behind the singers, a scaled-down SPCO of 10 string players traced the sparely written textures of Pergolesi's intimate accompaniment. Cohen probed and guided the musicians from a mellow chamber organ, distilling an atmosphere of mournful contemplation and private grieving.

Cohen, the most recent addition to the SPCO's roster of artistic partners, earlier had shown why he is renowned as a specialist in baroque music, in a probing, sensually shaped reading of Locatelli's Concerto Grosso in E-flat, Op. 7.

There, and in the Haydn symphony (No. 7, "Noon") that followed, concertmaster Ruggero Allifranchini made scintillating, richly imaginative contributions in the numerous passages for solo violin provided by both composers.

Allifranchini's trading of string licks in the symphony's second movement cadenza with the lithe, incisive cello of Julie Albers was a highlight. So too were the warbling flute solos and a scampering double bass spotlight from Zachary Cohen in the Menuetto's trio section.

Cohen directed the Haydn from a harpsichord, with quiet aplomb and watchfulness. His artistic partnership with the SPCO is in its infancy, but early signs are that the orchestra has made yet another highly astute signing.

Terry Blain writes about classical music and theater.