Monday in the Paschal Octave is a double of the first class and formerly a holyday.
The Office is essentially the same as the feast of Easter with some parts proper to the day. At Mattins the invitatory, antiphons and psalms (1, 2 & 3) are sung as yesterday. The three lessons and responsories are proper. The Te Deum is sung to the solemn tone where possible. At Lauds the same antiphons and psalms are sung as yesterday. The Haec dies is sung as yesterday in place of the chapter and hymn. The antiphon on the Benedictus and the collect are proper to the day.
At Prime and the Hours festal psalmody is sung to the special Paschal Tone 2 chant.
Mass is sung after Terce. The Mass is proper. The Gloria is sung, the Creed is sung, the preface is of Easter, the Communicantes and Hanc igitur in the Canon are of Easter. Again Ite, missa est, alleluia, alleluia is the dismissal.
Vespers are as on the feast. The antiphon on the Magnificat and collect are proper.
The celebration is so high-ranking that St. Vincent Ferrer is not celebrated this year (in the pre-1911 system his feast would have been transferred). His feast was mentioned yesterday of course in the Martyrology.