Honestly, it was about as exquisitely, sublimely beautiful a musical experience as I have had in a long, long time.

I didn't go with high hopes. It was a cold and dismal October afternoon, and the rain had seeped through my bones to my heart. And the promise of a local a cappella ensemble singing Dufay, Josquin, Gesualdo, and Palestrina did not raise my hopes. Surely the singers would inevitably go flat, the tempos drag. Surely they would start on one tone and inexorably end at least a half tone below. Surely singing such deeply expressive and profoundly spiritual music would be beyond them.

Surely, I was wrong. Vox, the local a cappella ensemble in question, can in fact sing those composers' gorgeous and glorious music, and they don't go flat, get lost, or drop dead. They sing with security and confidence; they sing in tune and on time. They sing line against line of chromatic counterpoint with only one voice to a part, and they sing it with extraordinary beauty of tone. My skepticism was confounded. They were terrific.

Vox's opening set of sixteenth- and seventeenth-century madrigals was deeply expressive. I thought I would expire from the heart-rending beauty of Monteverdi's "Si ch'io vorrei morire." But then came Gesualdo's "Itene, o miei sospiri," with its anguished and agonizing chromatic harmonies, and I thought certainly my heart would break. Their performances of sacred motets by Dufay and Josquin, two of the loftiest and noblest composers before Bach, also found an ethereal purity of tone and celestial clarity of voice.

But as good as the madrigals and the motets were, they were merely the prologue to Palestrina's Pope Marcellus Mass. Although Palestrina is far from my favorite composer of polyphonic masses — give me Ockeghem or Josquin — Vox's performance was simply stunning. The ease of their ensemble, the assurance of their intonation, the gracefulness of the rhythm, the beauty of their tone: these things could be taken for granted. The calm concentration, the tranquil intensity, the still sublimity of their Pope Marcellus was sweet joy.

Vox's season concludes with a concert of Renaissance elegies on Saturday, March 9, at St. Thomas the Apostle Church. Don't miss it.