Part prayer, part meditation, a concert by the David York Ensemble slowed time to a trickle, Saturday. For which we gave thanks, particularly at this time of year. With Henryk Gorecki's slow-motion "Miserere" as the centerpiece, the choir brought skill and poise to music that demanded sustained intensity.

David York's choir has been around for two decades, but recent changes have slimmed and improved it. The sound was vivid and focused, with a particularly nice soprano blend. Led by York, himself, the 16-voice group offered subtle, shaded performances of challenging music.

The program in reverberant St. Mary's Cathedral began with a medieval chant by Hildegard von Bingen. Led by soprano Maria Karlin, the past filled the present as a handful of women sang of celestial light with grave, yet alert, voices.

Using the same text, composer Joan Andrews replaced Hildegard's spare unisons with gentle, contemporary harmonies.

York, who is also a composer, led three movements of his own oratorio, "Mother of Us All," which he premiered with the Concord Choir almost 16 years ago. With simple, direct lyrics by Portland poet Judith Barrington, the work asks us to remember the female aspect in the spiritual and natural worlds.

As it moved from chordal harmonies to overlapping lines to pop chords and a great swell of polyphonic textures, the unaccompanied music made a lively, attractive impression.

Gorecki's "Miserere" is 30 minutes of very quiet, very simple, music that resembles a great sonic arch, but with no regular, perceptible meter. Rather, eight choral parts enter in turn over a period of 20 minutes, singing just three words: "Domine Deus noster" ("Lord Our God").

We hear gradual growth and development until, at the climax, eight parts increase to 10 before sinking back. Only in the last few minutes do the singers utter the work's central words, "Miserere nobis" ("Have Mercy on Us").

No matter what your belief, the Polish composer Gorecki -- like J.S. Bach -- is a composer of spiritual persuasiveness. The prolonged pleas of "Miserere," written in response to a violent 1981 protest in Poland, came to feel like holy stillness.

Quiet singing is one of the hardest tasks for a choir, but the singers remained steady and poised. If you haven't heard the David York Ensemble for a while, it's time to catch up. Their next concert is Feb. 8.