Officium Defunctorum (Victoria)

Officium Defunctorum is a musical setting of the Office of the Dead composed by the Spanish Renaissance composer Tomás Luis de Victoria in 1603. The texts have also been set by other composers including Morales.
Victoria includes settings of the movements of the Requiem Mass, accounting for about 26 minutes of the 42 minute composition, and the work is sometimes referred to as Victoria's "Requiem". However, it is not his only requiem, in 1583, Victoria composed and published a book of Masses, reprinted in 1592, including a "Missa pro defunctis" for four-part choir.
History.
From the 1580s Victoria worked at a convent in Madrid where he served as chaplain to the Dowager Empress Maria, sister of Philip II of Spain, daughter of Charles V, wife of Maximilian II and mother of two emperors. 
"Officium Defunctorum" was composed for the funeral of the Empress Maria.
She died on February 26, 1603 and the great obsequies were performed on April 22 and 23.
Publication.
Victoria published eleven volumes of his music during his lifetime, representing the majority of his compositional output. "Officium Defunctorum", the only work to be published by itself, was the eleventh volume and the last work Victoria published. It was dedicated to Princess Margaret, who was a nun in the same convent as her mother, for “the obsequies of your most revered mother”. The date of publication, 1605, is often included with the title to differentiate the "Officium Defunctorum" from Victoria's other setting of the Requiem Mass.
Structure.
"Officium Defunctorum" is scored for six-part SSATTB chorus. It was possibly intended to be sung with two singers to each part.
It includes an entire Office of the Dead: in addition to a Requiem Mass, Victoria sets an extra-liturgical funeral motet, a lesson that belongs to Matins (scored for only SATB and not always included in concert performances), and the ceremony of Absolution which follows the Mass. Polyphonic sections are separated by unaccompanied chant incipits Victoria printed himself. The Soprano II usually carries the cantus firmus, though "it very often disappears into the surrounding part-writing since the chant does not move as slowly as most cantus firmus parts and the polyphony does not generally move very fast." The sections of the work are as follows: