That song is Miserere Mei, a falsobordone setting (setting being the setting of a psalm to music, falsobordone being a style of musical recitation in the 15th-18th centuries) of Psalm 51, written by Gregorio Allegri around 1638.
I first heard the piece at a local choral concert with a friend--its strong melodies and haunting harmonies stuck in my mind, and I underlined it in the program to look up when I got home. Although I've since listened to it repeatedly, I never knew anything about it until this morning, when I looked it up to share with you.
Allegri (1582-1652), an Italian priest and composer, wrote the work "on his own time"--or rather, not for a particular commission. Soon, however, his music caught the ear of Pope Urban VIII, who secured an appointment for him in the choir of the Sistine Chapel. He held this position until his death.
The Miserere itself offers a double-choir version of Psalm 51; one choir sings it chant-style and the other adds melodic embellishment...this is what creates that exquisite tapestry of sound. At some point after its writing (and for unknown reasons), the Misererei was forbidden to be transcribed and published (!!!) and allowed to be sung only in the Sistine Chapel itself.
This continued until, as legend has it, a young composer by the name of Mozart visited the Sistine Chapel in 1770. After hearing the piece only twice, he transcribed it accurately from memory and took it home. Since then, the piece has spread through the world, with ornamentation added by performers until became what it is today.
Sharing it with you today is an appropriate coincidence, as the piece was traditionally performed during Holy Week back in the Sistine Chapel days. Here, the King's College Choir gives it at Easter, in the King's College chapel:
Psalm 51 itself holds one of my favorite verses, and many more that have been a mainstay of the Church for millenia:
"Create in me a clean heart, O God; and renew a right spirit within me. Cast me not away from thy presence; and take not thy holy spirit from me." Psalm 51:10-11What a beautiful ode Miserere is to this heart-felt, repentant Psalm. The Psalmist earnestly desires to serve the Lord with a pure heart, not half-way and steeped in sin. Praise the Lord for His incredible sacrifice at the Cross--the meaning of Easter, and the reason this song was sung--which enables us to live that Spirit-given, Spirit-filled victory over sin! I pray this song blesses you as much as it did me.