First Thursday vacat
Three Masses proper, as Requiem Masses with the rubrics of the same.
Every priest may say three Masses this day and three proper Mass texts are given. Whoever celebrates only one Mass uses the first Mass; the same applies to those who celebrate a sung Mass, with the ability to anticipate the second and third Masses if they are Low. Whoever celebrates three Masses without interruption is obliged to say the sequence Dies irae in the principal or first Mass; in the other Masses, unless sung, he may omit it.
Regarding the particular ceremonies involved when two or three Masses are celebrated within a short time frame, see the rubrics of Trination. When one Mass follows another without pause, the prayers after Low Mass are omitted, to be said only after the final Mass of the series.
The intention of the first Mass is for All the Faithful Departed; that of the second is for any particular intention (from among the faithful departed); that of the third is ad mentem Summi Pontificis; a stipend may be retained only for the Mass celebrated for the particular intention, any other stipend is alienated.
The Office is all proper, with some particular variations as noted in the Breviary. Requiem aeternam is said in lieu of the Gloria Patri in the psalms and responsories; there are no hymns; the introduction to each hour (Deus in adiutorium, etc.) is omitted
Matins: All proper, no hymn; no Te Deum
Lauds: All proper; no chapter or hymn; Pater noster and a truncated conclusion
Prime: All proper; no hymn; Pater noster and a truncated conclusion; chapter office abbreviated and particular
Hours: All proper; no hymn; Pater noster and a truncated conclusion
Vespers: All proper; no chapter or hymn; Pater noster and a truncated conclusion
Compline: Confiteor and absolution immediately, then psalms; no hymn; Pater noster and a truncated conclusion; no Marian antiphon