Today is September Ember Wednesday, or sometimes referred to as the Michaelmas Ember Wednesday. The Ember Day is commemorated in the Office and Mass of SS Cornelius and Cyprian whose feast is of semi-double rite. The Ember Days are ancient liturgical celebrations and, traditionally, times of fasting and penance. It seems the Christians in Rome developed these penitential practices from a very early period and, rather like Lent, the days developed their own liturgical character. Ember Saturdays, in particular, were days when ordinations took place, along with the Vigils of Easter and Pentecost.
At Mattins the scriptural lessons in the first nocturn are taken from Monday when they could not be read because of the feast of the Exaltation of the Holy Cross. A rubric in the Breviarium Romanum after the third Sunday of September states that if the lessons of Monday and Tuesday cannot be read on their appointed day and that on one of the Ember Days (which don't have Scriptural lessons) a feast occurs then rather than having recourse to the Common of that feast the lessons for Monday and/or Tuesday are transferred. So today Monday's lessons are read with the responsories of Wednesday. In the second nocturn the lessons three and four are historical ones for St. Cornelius Pope and Martyr and the sixth from St. Jerome's writings on St Cyprian. In the third nocturn the homily is from St. Gregory and the ninth lesson is of the commemorated Ember Wednesday. (All three lessons of the Ember Day may be read as one).
At Lauds a commemoration of the Ember Wednesday is sung, its antiphon on the Benedictus and collect are proper, and also of SS Euphemia, Lucy and Geminianus (if today were not an Ember Day then a ninth lesson of these martyrs would have been read).
Mass is sung after Terce. The Gloria is sung, the second collect is of the Ember Wednesday, the third collect of SS Euphemia etc. The last Gospel is of the Ember Wednesday. Private Masses may be of the Ember Wednesday celebrated in violet vestments with the deacon and subdeacon wearing folded chasubles rather than dalmatic and tunicle. There is no Gloria, an OT reading preceded by Flectamus genua and a collect, then after the 'main' collect SS Cornelius and Cyprian are commemorated followed by SS Euphemia etc. Benedicamus Domino is sung as the dismissal.
In Cathedral and Collegiate Churches two Masses are celebrated. The Mass of the feast takes place after Terce with a commemoration of SS Euphemia, but not the Ember Day, and with the third collect A cunctis. The Mass of the Ember Day is sung after None with the second collect A cunctis and third at the choice of the Dean and Benedicamus Domino as the dismissal.
Vespers are of the following feast of the Impression of the Stigmata of St Francis with a commemoration of the preceding Office.
In the 'liturgical books of 1962' Ember Wednesday is postponed a week due to the novel way introduced of calculating the first Sunday of the month. SS Cornelius and Cyprian are cut down to a third class feast with three lessons. The occurring Scripture is what traditionalists read last Wednesday. SS Euphemia etc get a commemoration at Lauds and Low Mass. Vespers are of SS Cornelius and Cyprian without any commemorations.