I often find that the lectionary Psalm and gradual don't correspond. Yes, I do believe the MR and LfM are working against the Graduale Romanum, or rather the compilers of the MR and LfM were. GIRM 61 says, "The responsorial Psalm should correspond to each reading and should, as a rule, be taken from the Lectionary." Whereas the GR and GS contain the first option for the entrance chant, such is not the case for the Responsorial Psalm, and I don't think that such is the case for spoken masses only. Missalettes follow the LfM. Although I have complaints against the N.O. lectionary, the inclusion of the responsorial psalm at the expense of the gradual isn't one of them.

Although the official rationale has to do with the distinction between sung and read Masses (see the Tietze article), I think there's more to the story here.

Bugnini, in his memoir of the reform, recounts the process by which this change came about. (I don't have the book in front of me, just going by memory). A number of council Fathers were polled for feedback on whether certain proposed reforms to the missal were desirable. One of the questions they were asked was whether the Missal should include a selection of entrance and communion antiphons to be recited at read Masses "for spiritual fruit". Most of them responded that it sounded like a good idea. I imagine many of them were confused by the question, though. Bugnini also states that part of the intention was that these new texts would be the basis for musical compositions in the vernacular.

Here's my pet theory on what was going on behind the scenes: At the time with the new lectionary, there was a mismatch between the Graduale propers and the readings much of the time. The Ordo Cantus Missae, let's remember, didn't emerge until a few years after the Missal had been assembled. The compilers of the missal probably felt that there would never be a way to make the propers fit into the new lectionary, so they made their own propers to be models for translations, thinking Latin celebrations would be rare anyway. This was all put together rather hurriedly, though. When the Ordo Cantus Missae emerged (the work of Benedictine monks, I think), it turned out that the compilers of that work had done an excellent job arranging the antiphons in the existing repertory to fit the new lectionary -- often, particularly in the case of the Communion antiphons, they fit better than what the compilers of the Missal proposed!

I would be very interested in learning who assigned the Gregorian Propers to the New Mass.

Has anybody else noticed that this year, the chant propers for ordinary time (1970 Missal) and after Pentecost (1962 Missal) seem to be in synch? I just noticed it last week, when the propers for the 25th Sunday of Ordinary time are the same as those for the 19th Sunday after Pentecost. Comparing the older and newer Roman Graduals, there's a long stretch of Sundays where they match. I wonder how often that happens? Maybe it has to do with this year's very early Easter? I did know that the propers for the newer Mass uses sets of propers from the older in many cases.

This Sunday, the correspondence is less complete than last Sunday, because both the Introit (In nomine Domini)and Gradual (Christus factus est) for year A use texts from the Philippians epistle read in year A. In years B and C, the 26th Sunday OT and 20th Sunday after Pentecost match.

Am I wrong in thinking that the readings from the 1962 missal have a better chance of being left in place during cycle A than the other two Sunday cycles? I haven't made an exhaustive comparison, but that may be a reason that the propers seem to be fitting the readings this year? Let me know civily if I'm making an unintelligent comment.

Even when the old lectionary was in use, any connection between the proper chants and the readings assigned to the Sundays after Pentecost was coincidental.

The introits, for example, consist largely of extracts from the psalms arranged in numerical sequence (with gaps, of course). This arbitrary sequence partly survives in the Ordo Cantus Missae scheme on which the 1974 GR is based.

Even when the proper chants reflect the "theme" of the day (e.g., at Christmas) they are seldom related directly to the readings.

Throughout the year direct connection between chants and readings has primarily been confined to communion antiphons and alleluia verses. OCM probably increased the number of occasions when a connection between a chant and a reading is evident.