This will probably be an unpopular opinion, but I suggest playing around with the accompaniment and develop a skill for improvising accompaniments. So long as it supports the singing, I would find that completely appropriate. Practice improvising the same chant a few keys up and a few keys down.

I shall await patiently now for disagreeing opinions.

Of course I would like to develop the ability to improvise accompaniment, but yes I’m not at the stage to just start doing it - total beginner organist here! Some familiarity with the idiom would be good as a starting point.
And yes I mean Latin psalm tones, I chant ‘62’s office. To be honest I don’t really like the Meinrad tones, but I think that’s just personal preference, and in any case they’re not for the office I’m trying to accompany.

There are accompaniments, if you are doing 1962 or earlier, for the office of Vespers (and Compline) on Sundays and feasts.

I use Henri Potiron’s accompaniment available from the Lalande library on Corpus Christi Watershed’s site. Now, for the psalms, I do a bit of violence, because our organist needs the verses written in full, so I don’t have any accommodation for a dactyl versus a spondee where the notes change differently. But the ideal is to learn the psalter well enough to follow from your Liber (or the antiphonal, or a copy) and not need to have each syllable attached to a note of organ music. Anyway, I take the Potiron and make full scores in Musescore Studio, of which I have PDFs of every office done so far in the past two to three years, plus the Magnificats in every tone used at Sunday Vespers (simple and solemn; luckily it’s a lot of copy, paste, drag notes up or down).

I think that it is worth learning to drop the melody of psalmody except when accompanying the congregation (we do cantors-all…) and on the more difficult psalm tones (3a2, 4E) as needed. Otherwise, just do the chords.

Always, always, always, accompany the incipit when sung solo, just the chords, including the opening Deus in adjutorium or the incipit of the hymn etc. Listen to Fontgombault even if you don’t do everything like them (see the next point).

Other people prefer the NOH, but not only do we use the Solesmes editions and not the Vatican rhythm, I don’t care for the NOH.

But on improvising: no matter the rhythmic school, the Fontgombault system of writing in the number of sharps or flats plus the first note (but not specifying a key signature exactly, since you will otherwise have some problems) is helpful, and then there a few different treatises available.

Some people here like Dom Claire’s accompaniment from Solesmes much later in the 20th century. The PDF is posted somewhere here.

In my organ resources page you will find all the printable PDFs of all year round 62's Vespers (both in individual files and also compiled in larger ones) and Compline plus Mass ordinaries and responses (and some other stuff) that I myself (pianist converted to organist without much capability to improvise but to sightread) made using the resources already mentioned by others here to be able to accompany chant at my parish. File titles are in Spanish (browser translator would do), but chant is, naturally, all in latin.

@MatthewRoth You must be talking about an old file of mine! Is that one/s you mention in my organ resources page? (For they should be not!)

When I began accompanying chant at home I used to play on a keyboard with a transposer so I did not mind about the score, but since I moved to the actual church where we have a pipe organ (it is been two years and a half now) I had to transpose all of those B flat scores to A, for I also prefer as you say, singing the whole Office in A. Exception are those mentioned by you: hymns and short responsories plus, in my case, the proper of the time's Magnificat antiphons which I took from Julius Bas' accompaniment books -Potiron only has Sundays and feasts- and were way too many to tranpose each of them.

Therefore, I thought all the Office files I uploaded to the organ resources page were updated versions with psalmody in A, but maybe I missed some without noticing. Could you be so kind to tell me which one/s you found with B flat psalmody, so I can fix them (whenever you have the time)? Thank you very much!

The NOH is a pretty good turn-key solution and has examples of accompaniment for the psalm tones, though it doesn't include antiphons for the liturgy of the hours.

It’s a lot of work if you don’t use the Vatican rhythm.

I have an accompaniment which was put together from recent studies under the solesmes school. I can take photos if you are interested.

@MatthewJ
There’s no regular accompanied chant Masses within a 2 hour drive, NO or EF, so no experts here unfortunately! I know one guy who does some chant accompanying so I can ask him, but he doesn’t do any improv accompanying and has no experience with the office. I’m going to university this year so I may have access to some teaching around there.

@DOAdvocate I will send you a PM later today

To my ear, the NOH is just a little too jazzy;

ok yeah… I will admit it is that… and I do love jazz!

Modes are modal and jazz is modal. Modes is the thing… being modal is the important thing. Almost all the other accomps are built on major and minor scales. They kind of are the more modern version of chant accomp.

I would like to see fontgombault in print and be able to analyze it structure.

@Charles_Weaver please do.

I didn’t appreciate chant accompaniment until learning chant under Nick Botkins when he was in STL. It grew on me.

@MatthewRoth Thank you very much for the heads-up! I have learned it wrong then, since the priests for whom I work have never sung the ferial tone, only the festal and solemn ones (they are diocesan priests, they must have learned it wrong too).

Then, when celebrating a feria, in Vespers, both the Deus in adjutorium and the prayer should be in ferial tone? Or only the Deus in adjutorium? I mean, for instance, in Compline, the Deus in adjutorium is always in the ferial tone, but the prayer is the festal one (la-fa#), is not it? The ferial tone for the prayer would be this one which is almost recto tono?

Thanks in advance!