Aggie Catholics has posted their annual pre-Lent resource. Among the various links, they had posted a YouTube clip of the Tallis Scholars singing Gregorio Allegri's "Miserere mei". Alas, it stops just over 2/3rds of the way through. Fortunately, I found another clip that has the whole piece:
"Miserere mei" is based on the Latin text of Psalm 51 (50), which is a part of the tenebrae liturgy of Holy Week. It has two choruses comprising nine voices, with a tenth voice chanting every second or third verse in plainsong. Allegri composed it to be performed in the Basilica of St. Peter's, taking advantage of its marvelous acoustics.
The result is so powerful that, for many years (so the story goes), the Vatican kept only two or three copies under lock and key, and forbade its performance anywhere else under pain of excommunication. The ban was lifted shortly after a fourteen-year-old Austrian freak named Wolfgang Amadeus Mozart copied it down from memory after one hearing, listening to it a second time only to correct some minor errors; instead of casting him out, the Pope praised the young Mozart for his genius.
When I listened to it for the first time, "Miserere mei" reminded me of another fine example of Renaissance polyphony that I performed with my high school chorus and with the NMEA All-State Chorus in 1981, Giovanni Gabrieli's "O magnum mysterium". So you get a two-fer: Here's the latter piece, performed by the Tallis Singers of Toronto:
Just a couple more examples of Catholicism's rich cultural heritage and legacy.