Miserere Mei Deus.

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Fifteen candles on the Tenebrae "hearse".

The candles are extinguished, one by one,

during the course of the Service.

Deutsch: Triangel Leuchter (Tenebrae-Leuchter) 

im Mainzer Dom.

English: Tenebrae "hearse" (candelabrum), 

used during Holy Week, Mainz Cathedral.

Photo: 9 April 2009.

Source: Own work.

Author: Bhuck.

(Wikimedia Commons)

Miserere Mei Deus.

Available on YouTube at

http://youtu.be/zC0o723hb0M.

Miserere, (full title: Miserere mei, Deus, Latin for "Have mercy on me, O God") by Italian composer Gregorio Allegri, is a setting of Psalm 51 (50) composed during the reign of Pope Urban VIII, probably during the 1630s, for use in the Sistine Chapel during Matins, as part of the exclusive Tenebrae Service on Holy Wednesday and Good Friday, of Holy Week.

The Miserere is written for two Choirs, one of five and one of four voices, and is an example of Renaissance polyphony surviving to the present day. One of the Choirs sings a simple version of the original Miserere Chant; the other, spatially separated, sings an ornamented "commentary" on this. 

The piece is an example of the stile antico or prima pratica; however, its constant use of the dominant seventh chord, and its emphasis on polychoral techniques, certainly put it out of the range of prima pratica; a more accurate comparison would be to the works of Giovanni Gabrieli.

The Tenebrae Service, where the Miserere would be sung, normally began at around 3 A.M. During the Ritual, candles would be extinguished, one by one, save for the last candle, which remained alight and was then hidden. Allegri composed his setting of the Miserere for the final act within the first Lesson of the Tenebrae Service.

It was the last of twelve falsobordone Miserere settings, composed and chanted at the Service since 1514, and is the most popular: at some point, it became forbidden to transcribe the music and it was allowed to be performed only at those particular Services, thus adding to the mystery surrounding it. 

Writing it down or performing it elsewhere was punishable by excommunication. The setting that escaped from the Vatican is actually a conflation of verses set by Gregorio Allegri, around 1638, and Tommaso Bai (also spelled "Baj"; 1650–1718) in 1714.