- I only know of a Benedictine lectionary in French or Latin-French. That said, the lectionary in the 4-volume LOTH is approved for both Benedictine and Roman Offices. You could use it, and for the patristic reading you could substitute readings from monastic sources.
- There are a few things you can do; you can use the current LOTH and add monastic touches. A couple of examples, using psalm 4, 90 and 133 for compline every night (permitted, see General Instructions), directly without antiphon; add the “Kyrie Eleison” between the intercessions and the Pater, and add the traditional invocations for the deceased faithful and absent brothers after the final blessing. O**r you can use one of the 4 approved Benedictine psalter schemas as described in the Thesaurus Liturgia Horarum Monasticae. ** On weekdays you could use Ps. 66(67) as invitatory, as that psalm starts Lauds of the Benedictine Office every day (the invitatory is 94(95)), especially if you start with Lauds every day.
- Sort of. One, it’s incomplete and does not have the propers and ordinary for saints; it’s missing most of the music for seasons too. If you pray day hours only, a much better bet would be Antiphonale Monasticum (from the same website); Vol I for the proper of the seasons, Volume II for the diurnal psalter, Vol. III for the saints (Volume IV, if it ever comes out will be the night office, and Vol. V is the proper of the Solesmes Congregation only). With respect to using Psalterium Monasticum as psalter for the LOTH, the psalms are in the Neo Vulgate and thus are liturgical; the antiphons are liturgical; it only has one cycle of readings instead of 4 like the LOTH; to be liturgical you could use the readings from the LOTH. However a major departure is for the seasons and the proper antiphons of Sunday: the Benedictine Office uses three different antiphons for the Gospel canticle for 1st Vespers (matched to the readings of the one or two year cycles for Vigils), one for Lauds (Benedictus), and one for 2nd Vespers, whereas the LOTH uses the same antiphon for all three.
But since the General Instructions do allow substitutions (for example you can substitute an antiphon or hymn for another from the same season), some latitude is OK.
If you are an oblate you can follow the Benedictine calendar, but if not you should probably pray the General Roman+local calendar for your diocese.
My own personal opinion, FWIW, is that praying the Psalterium Monasticum, especially if you pray Vigils, is fairly heavy going for laity or people living/working in the secular world (including… maybe especially for… clergy); it’s 250 psalms a week; Sunday/Festive Vigils is 3 nocturnes and takes over 1 hour to pray properly. It’s easy to get into LOTH overload that way.
I prefer praying the current LOTH but with the Benedictine touches I mention in 2 above. Occasionally when I feel a bit more ambitious I’ll pray the schema the abbey I’m associated with uses (Schema B, 150 psalms in a week with no repetitions; Vigils is much lighter with only 6 psalms, 3 per nocturne, rather than 12, 6 per nocturne).
Since I’m into Gregorian chant in a big way, I chant my Offices except for Vigils (Office of Readings) which I chant recto-tono. I use
Les Heures Grégoriennes; it’s beautifully done and very practical for choral use, it includes
all of the Latin music for the day hours of the LOTH including Compline; the music is from the monks of Solesmes. The Latin is side-by-side with French. Worth every penny and comes in three volumes (Advent-Christmas-Ordinary Time; Lent-Eastertide; Saints), and you can get an optional CD that has recordings of the first strophes of every hymn, every antiphon, and the first verses of every psalm.
I also use
Antiphonale Romanum II, Latin only, Vespers for all Sundays, feasts and solemnities. The big advantage for newbies to chant is that the psalms are all pointed for chant. Les Heures Grégoriennes assumes you know how to psalmody.
Edit: forgot to mention that for monks, the General Instructions of the
Monastic Liturgy of the Hours allows monks who are outside the monastery, or engaged in heavy apostolates, to substitute the Roman LOTH (4-week schema); so even monks are not bound to their monastic office when outside the cloister. Individual monasteries may also use the 4-week LOTH with special permission (but would still follow the Benedictine calendar). Otherwise monks are bound to say at least 75 psalms a week. Our abbey does the whole psalter in a week.