The feast of SS. Nereus and Companions is of semi-double rite. Today is also the Vigil of the Ascension and the last day, the Wednesday, of the Rogations or Lesser Litanies.
At Mattins the lessons in the first nocturn are Fratres: Debitores, taken from the Common of Martrys in Paschaltide. In the third nocturn the ninth lesson is a homily for the Vigil (its three lessons may be read as one)from St. Augustine. At Lauds a commemoration of the Vigil is sung (the antiphon on the Benedictus is proper, the prayer from the preceding Sunday) and the Commemoration of the Cross is sung.
At the Little Hours the Paschaltide Doxology and tone is sung at the hymns (for the last time this year). At Prime the Dominical preces are sung. The first entry in the Martyrology is the announcement of the feast of the Ascension tomorrow.
Mass follows Terce. The Gloria is sung the second collect is of the Vigil, the third of the Rogations, the Paschaltide preface is sung (for the last time this year) and the last Gospel is of the Vigil. Private Masses may be of the Vigil, the Gloria is sung, the second collect is of SS Nereus and Companions and the third collect that of the Rogations, the preface is of Paschaltide and, unusually for a Vigil, the vestments are white.
Where the Rogation Procession takes place and there is only one Mass it is sung after None. The antiphon Exsurge Domine is sung by the cantors and then the Litany of the Saints is sung: each invocation and its response being sung by the cantors and then repated by the choir. The celebrant wears a violet cope, the deacon and subdeacon violet dalmatic and tunicle respectively. When Sancta Maria, ora pro nobis has been sung all rise and the Cross-bearer leads the Procession accompanied by acolytes carrying candles followed by the cantors, choir and the ministers. The people follow. The Procession should, in theory, go around the parish with the Litany being repeated if necessary or the Penitential and Gradual Psalms added if the distance requires them. After the Procession re-enters the church the psalm Deus in adjutorium is sung and all kneel, the celebrant rises to sing the following ten collects. The Mass Exaudivit follows sung in ferial tones with violet vestments. The Gloria is not sung, the second collect is of SS Nereus, the third of the Vigil, Benedicamus Domino as the dismissal and last Gospel of the Vigil.
In Cathedral and Collegiate Churches three Masses are celebrated: one of the Vigil, one of the feast and the Rogation Mass after the Procession. In the Rogation Mass the second collect is Concede nos, the third collect Ecclesiae.
First Vespers of the great feast of the Ascension are Sung. At Compline and the other Hours hymns of Iambic metre have the Ascensiontide Doxology: Jesu tibi sit gloria, Qui victor in caelum redis, Cum Patre et almo Spiritu, In sempiterna saecula. Amen.
Following the 'liturgical books of 1962' the Vigil has been raised in rank to II class and takes precedence over SS Nereus and Companions. St. Nereus is commemorated at Lauds, the Commemoration of the Cross is suppressed. At the Hours the Paschaltide Doxology and tone are not sung for the hymns, at Prime the Dominical preces are omitted. St. Nereus is commemorated in Low Mass.
Where a Procession takes place the Litany is not duplicated and may be in the vernacular. At the votive Mass following the 'preparatory prayers' are suppressed, the Vigil is commemorated but not St. Nereus, Ite missa est is sung as the dismissal. The Doxology of the Ascension is not sung at Compline or the other Little Hours.