From this page on Zenit (http://www.zenit.org/en/articles/com...ints-in-lent):
Regarding the Liturgy of the Hours, the General Introduction to the Divine Office says:
"Memorials During Privileged Seasons
"237. On Sundays, solemnities, and feasts, on Ash Wednesday, during Holy Week, and during the octave of Easter, memorials that happen to fall on these days are disregarded.
"238. On the weekdays from 17 to 24 December, during the octave of Christmas, and on the weekdays of Lent, no obligatory memorials are celebrated, even in particular calendars. When any happen to fall during Lent in a given year, they are treated as optional memorials.
"239. During privileged seasons, if it is desired to celebrate the office of a saint on a day assigned to his or her memorial:
"a. in the office of readings, after the patristic reading (with its responsory) from the Proper of Seasons, a proper reading about the saint (with its responsory) may follow, with the concluding prayer of the saint;
"b. at morning prayer and evening prayer, the ending of the concluding prayer may be omitted and the saint's antiphon (from the proper or common) and prayer may be added."
Later are some specific norms for special seasons:
"247. In the office for Sundays, solemnities, feasts of the Lord listed in the General Calendar, the weekdays of Lent and Holy Week, the days within the octaves of Easter and Christmas, and the weekdays from 17 to 24 December inclusive, it is never permissible to change the formularies that are proper or adapted to the celebration, such as antiphons, hymns, readings, responsories, prayers, and very often also the psalms.
"252. Everyone should be concerned to respect the complete cycle of the four-week psalter. Still, for spiritual or pastoral advantage, the psalms appointed for a particular day may be replaced with others from the same hour of a different day. There are also circumstances occasionally arising when it is permissible to choose suitable psalms and other texts in the way done for a votive office."
Thus, if morning prayer is united to Mass, then there is no change in the office at all on a commemoration. Everything would be taken from the day except the saint's collect at Mass.
As seen above, it is possible to change the psalms of the day while maintaining the proper Lenten antiphons. Making use of this option requires careful discernment and a liturgically literate community able to both understand the reason for the change and easily navigate the Book of Hours.