There are a number of issues to be worked out:
- Changes in the NO: Introit is joined to the Kyrie; Agnus Dei has different text ("qui tollis peccata mundi, dona eis requiem . . . sempiternam")
- As SponsaChrsti alludes to it, texts are modified or incomplete: Faure set only part of the offertory text to music, and the text he did set is modified; no "Benedictus" in the Sanctus

For the "Pie Jesu" and "Libera me," one could be placed at communion and the other as a prelude.

I just would not do it unless you’re told to do it or have no scruples left to give. Not to stir the pot, but I think that it does not make a lot of sense.

I used to work at a parish where we did the Fauré Requiem every year at a special Novus Ordo Mass on All Souls Day, as a commemoration of all the people who had died in the parish over the past twelve months.

It was celebrated like this:

— Introit (mvt.1) as Introit, but end it at the start of the Kyrie. Celebrant's greeting; spoken Confiteor by all, then
— Kyrie (mvt.1) as Kyrie
— after 1st reading, a choral Responsorial Psalm setting of Ps. 23 (wasn't by Fauré)
— after 2nd reading, the Pie Jesu (mvt.4) as a sequence before the Alleluia
— an Alleluia from the Graduale Simplex (verse in English — not by Fauré)
— O Domine Jesu Christe (mvt.2, the Offertoire) as Offertory
— Sanctus (mvt.3) as Sanctus
— Agnus Dei (mvt.5) as Agnus Dei, but end it before the start of the Lux aeterna.
— Lux aeterna (mvt.5) as Communion I, followed by
— Libera me (mvt.6) as Communion II
— In paradisum (mvt.7) as Recessional

There are a number of suitable settings of Ps. 23 at CCWatershed, here.

@trentonjconn I presume this was following MR2, where a suitable song could be sung before the Gospel. The DM at the Cathedral (Nick Gale RIP) would use a suitable song, it would just happen to be one of the former sequences appointed for the day.

Licit I think not, although it would be very far from the worst thing to happen at a N.O. Requiem.

I tend to agree with Matthew Roth. The Faure, (including many of the other large scale requiems) often diverge from the official text. In my mind they really are just concert pieces

As someone who sings in a professional chorus and performs such music, I wouldn’t even want that at Mass. I prefer the traditional Latin Requiem Propers, over these elaborate Requiem Masses. They don’t even make any liturgical sense. The style doesn’t fit the function or texts.

But note that the OP refers specifically to All Souls day. We are not considering a funeral. And Fauré was wanting to write something quite different from the Gregorian Requiem, with which he was of course very familiar.

As to my Requiem, perhaps I have also instinctively sought to escape from what is thought right and proper, after all the years of accompanying burial services on the organ! I know it all by heart. I wanted to write something different.

That suggests that he was the accompanist, but given what he actually composed (i.e. something not really usable at the high Mass), it’s not clear what he was actually doing (like, what I really want to know is what Mocquereau or even Pothier thought of the “right and proper practice at the time”…)

I am considering doing this for our All Souls Day mass of remembrance, along similar lines to what @CGM lays out above, though probably minus the Pie Jesu “sequence.” I’d prefer some other use for the Pie Jesu, perhaps as a post-communion meditation.

That being said, I also tend to agree Fauré’s setting is probably not the best to use for mass, if we’re looking for settings other than the original chants. In that genre, I would far prefer the Duruflé Requiem, though it is a tad more difficult both for the choir and the organ.