The Estonian Philharmonic Chamber Choir has built its fame on a unique sonority of pristine brilliance and diamond-hard clarity. Don’t look for the warm, rounded English sound or the sensuous French approach here, much less a gregarious American choral sound.

Friday’s concert at the Carlsen Center featured the 26-voice choir a cappella, conducted by Paul Hillier. Dressed in pastels and blacks, they looked as “cool” as they sounded. But when it came to music they were all business.

The program was a chance to hear some of the less-current unaccompanied works (or works with organ alone) by Estonian composer Arvo Pärt (b. 1935), whose austere, repetitive music is ideal for the choir’s gleaming, unflinching sonority.

Pärt has made a sensation among young listeners 20 years ago, and his newer works indicate that his inspiration remains sure. One highlight Saturday was the 2004 “Anthem of St. John the Baptist” for choir and organ, which juxtaposed explosive chords with a suave, full-bodied lyrical strains, which never shied from the subtly hypnotic effects for which Pärt is so well known.

Consistency of pitch and tone are this choir’s hallmarks. With tenacity it can sustain a pitch at any volume without altering the vowel or the tonal quality. Yet a hard-edged quality proved a liability in the first half, where Poulenc’s G-major Mass was at times pushed — with the “Agnus Dei” seeming more penetrating than lush or beautiful.

Four sections of the Rachmaninoff Vespers, Op. 39, were more idiomatic in approach — with the growling bass sound we associate with Russian choral sound. Yet there was still something unsettling in its lack of sentimentality.

The program’s second half was all-Pärt, and the choir was in its element. “Dopo la vittoria” showed the composer in a laconic mood, with pulsating narrative against an ever-shifting forward motion. The English-language “Littlemore Tractus” pitted a tiny organ motif against a full-bodied choral crescendo. “Triuvium” for organ alone, played by Christopher Bowers-Broadbent, showed that Renaissance counterpoint is still essential to Pärt’s art.

“Nunc dimittis” was an undulating expression of devotion, while the infectious dance-like lilt of the final “Salve Regina” had feet tapping. It felt like music of the ages, and it may well prove to be.