The voices of Anonymous 4 are matched with no music quite as perfectly as they are with the complexities of the 13th-century motet. The esteemed quartet’s 1994 recording of selections from this body of music, transcribed from the Montpellier Codex, was one of its best, and more than a decade later, the group still dazzles in this repertory. Its presence Friday made the Folger Consort’s New Year’s concert, an annual tradition at Washington National Cathedral, an instant musical highlight of the year to come.

To unravel the medieval motet’s tangle of voices, a knot of different texts and languages, these performances often began with just one texted voice’s part, with the others layered on gradually in repetition. Crystalline intonation and clarity of diction, without fussy exaggeration of the Latin, rarefied the pieces into limpid delicacies.

Four instrumentalists offered much simpler, strikingly understated performances of contemporaneous melodies, often the catchy tenors that were the basis of the motets on the program — an ingenious programming decision. The instrumental sound, including recorder, the breathy reed known as the douçaine and a charming, hand-pumped organetto, was delicate, perhaps too much so for the cathedral’s vast acoustic.

Monophonic music, adaptations of chants composed by Hildegard von Bingen, provided a meditative counterweight to the first half of evening. The 12th-century abbess and mystic was considered a saint in the Middle Ages, a status that Pope Benedict XVI will make official this year by canonizing her and naming her Doctor of the Church for her contributions to theology. That is really what sets her apart, more than her chant compositions.

The unison blend was not as pleasing as when the group sang polyphony, and individual voices showed some wear and tear. But overall, this was a performance worthy of the concert’s title, “Heavenly Revelations.”

Downey is a freelance writer.