This Misa de Difuntos consists out of the following movements:

01. Introito - Requiem aeternam
02. Kyrie - Kyrie, Christe, Kyrie
03. Gradual - Requiem aeternam, partly plainchant
04. Sequentia - Dies Irae
05. Offertorio - Domine Jesu Christe
06. Sanctus - Sanctus y Benedictus
07. Agnus Dei - Agnus Dei
08. Post communio - Lux Aeterna

It’s far unusual in the Renaissance to set a Missa pro defunctis for double choir but De Montemayor did. But in this Misa de Difuntos we are in the beginning of the Baroque period. There must be a reason for it to do so but that reason is unknown. De Montemayor sets this Requiem for double Choir in Venetian coro spezzato style, SSAT ( Primer coro) and SATB (Secundo coro) and figured continuo with Contrabajo. De Montamayor prescribed three Tiples in this Missa pro Defunctis, two in primer coro and one in secundo coro, that means there were in Monasterio de Nuestra Señora Guadalop enough talented young singers available. The highest note is f2.
Intoito.
Contralto of primer coro starts with quoting the plainchant ‘Requiem aeternam’ in long notes, Tiple 2, Tenor and Tiple 1 follow in a polyphonic way. In measure 4, secundo coro follows starting with Tenor, followed by Tiple, Bajo and Contralto. Many parts (Tenor, Tiple1 coro1 and Bajo , Contralto coro 2) start with a moving descending secunde f- es, whereas the other parts (Tiple2 primer coro, Tenor and Tiple coro 2) start with a descending secunde c-bes. As from measure 8, De Montemayor starts with the coro spezzato style where the two choirs answer each other’s. Imposing are the rhythmic phrases “et lux perpetua” (M. 18-22), which will shortly be repeated in (M. 29-30), ending in “Luceat at eis” with the two choirs together in F- major. De Montemayor seems a master in de the Coro spezazto style culminating with “Omnis caro veniet” in F-major.
From here starts again the beginning of this movement “Requiem Aeternam” ending dal signo S. De Montemayor prescribes here starts (at the end of measure 30) immediately the Kyrie (Al principio hasta la senal Y sigen los Kiries). This total movement has 104 measures.
Kyrie.
The Kyrie, Christe and Kyrie start in all movements in a polyphonic setting , culminating in each movement in coro spezzato style in F-major. This movement has 78 measures.
Gradual.
This gradual – chosen is for the “Requiem” - starts with the plainchant ‘Requiem aeternam dona eis Domine et lux perpetua luceat eis” followed in homophonic style with only the premer coro, first choir SSAT set in d-minor. This movement consists out of 36 measures. Dies Irae.
This Dies Irae is set in ¾ time, again with double choir, in coro spezzato style. As from measure 84 up to 92 De Montmayor starts with the introvert chosen polyphonic setting “Lacrimosa dies illa.” The second choir starts in bar 115 with “Pie Jesu Domine,” followed with a short polyphonic “Dona eis requiem” ending with the two choirs in “Amen” in d-minor. This imposing movement consists out of 131 measures.
Offertorio, Domine Jesu Christe
The Offertorio “Domine Jesu Christe” is again set for double choir in coro spezzato style, tempo ₵.
The composition is predominantly homophonic. Interesting is the “Libera animas omnium” (M. 13-24), set up in polyphonic style by primer coro culminating in homophonic style by secondo coro ending in A-major. The famous wording “Quam olim Abraae promisisti” is powerful set again in A-major (M. 74-82) and ending from A-major to d- minor (M. 100). De Montemayor omitted the sentence “Hositias et preces tibi” ending again in “Quam olim Abraae promisisti,” these sentence could be sung in plainchant.
Sanctus y Benedictus.
Premer coro starts this Sanctus followed by secundo coro both in a homophonic way. As from measure 7 ( M. 7-15) start two polyphonically motives g-↓d-e-f#-g (Bajo/c. 2) and a-bes-c-bes-a (Tenor/c. 2). Those motives are in alternate order started by the voices from Bajo/coro 2 up toTiple 1/ coro 1. (Also Bajo/coro 2 with the first motive followed by Tenor/coro2 with the second motive and so on up to Tiple 1/coro1 with motive 2). It’s an interesting musically building. After that the homophonic coro spezzato style is set by De Montemayor in using a-minor, F-major and d-minor. The Hosanna will start as from M. 37 by premer coro. As from M. 42 up to M. 48 De Montemayor sets five short coro spezzato passages ( each three half notes per coro) in “Hosanna” culminating in the closing “in excelsis” in d-minor. The Bendictus is note for note the same texture as De Montamayor sets in the Sanctus, due to the syllables in the text (for instance “in nomine’) the composer uses some more quarter notes.
Sanctus and Benedictus together consists out of 104 measures.
Agnus Dei.
Premer coro starts the first Agnus Dei with two different polyphonic imitative motives, followed by secondo coro with the same motives (M. 1 – 13), two short ascending lines and two short descending lines. De Montemayor uses again the coro spezzato style. Premer coro in homophonic style starts with some key-changes in the first “dona eis Requiem” ending in g-minor. Secundo coro answers in the same way with the second Agnus Dei. There is no third Agnus Dei. Premer coro answers thereafter with “Dona eis Requiem” ending in g-minor, which will answered by secondo coro ending in d-minor. The two coro follow each other in a three times “sempiternam” ending in a D-major. This movement has 37 bars. Post Communio.
Premer coro starts with an imitation (especially Tenor and Tiple 2 of coro 1) of the three first notes of the plainchant ” Lux aeterna” (descending a-g-f). Like we saw in the start of the Sanctus and Agnus Dei we see imitative style. Thereafter starts the homophonic coro speazzato style. In “Et lux perpetu lucet aeis” De Montemayor follows the syllables in the text in using quarter, quarter dotted and eighth notes. The choirs join together in “Quia pius es” from A-major ending in d- minor. This movement consists out of 47 measures. This Missa de Difuntos is found is the archives of San Lorenzo de El Escorial Madrid number 37784 and 39492, (later) publication in 1788 and 1808 by three copyists Castillo Lorezno in 1788 and by Juan Tomás Pagasatundúa around 1807-1808 and Jaime Ferrer (1762-1824) and further mentioned in Catálogo del Archivo de Música no. 18 and no. 1193 by Rubio.