There is no official source for music, as far as I know, so try asking Fr Samuel Weber OSB who has a wealth of material, like this - https://drive.google.com/file/d/1ShyspsvR2VTVF9Q64XFt_Cw2FSVOk21h/view Just ask him where to start, webersfl@gmail.com , or his current email is samuel(dot)weber(at)stpsu(dot)edu
For musically simplified Vespers (no through-composed antiphons) the Mundelein Psalter is a convenient ready-to-go solution. Similar results can be obtained free of charge by finding a suitable hymn tune, learning how to use some set of psalm tones and pointing psalm (+ antiphon and responsory) texts on your own.
If you are going for Vespers with through-composed antiphons, check this thread.
As for books you may be interested in "Dominican Prayer" (1994) and "Christian Prayer: ... edition with music" (1976).
A big issue with English liturgical texts is the copyright. We have to "pay to pray" in order to follow the official texts. I really wish the USCCB would simply add the liturgical texts to their website under a creative commons, so that composers could set the official texts to music provided they didn't alter them.
There are no official musical settings in English. Mundelein Psalter is good convenient resource if you have a group that regularly prays together and wants to chant using very simple tones. For a one time special event it's not so good. And if you want full settings of the antiphons you have to write them yourself or find something online such as mentioned above.
There's supposed to be a new edition of the Liturgy of the Hours published in the "near" future. At this point the Mundelein Psalter is nearly obsolete. I believe Source and Summit plans to offer some psalm tone options for the revised office once it is promulgated, but who knows how long before that is a reality.
Meanwhile, the official English language hymnal has been published through GIA. The Divine Office Hymnal.
Some other useful resources:
https://www.ebreviary.com/ ready made booklets or screen viewing options of the Official copyrighted texts. Some hours are free to view, but the complete office requires a subscription. Convenient if you want to print a booklet for a group. No music. Just text.
https://ibreviary.com/m2/breviario.php Unofficial, but seemingly the official texts. You could copy and paste the texts from here to design your own program and just proofread for typos or discrepancies. A huge time saver if you starting from scratch. No music. Just text.
I have resources if you send me your email in a private message. We pray in English in our community on weekdays and latin on feasts and solemnities. Free of charge! We are not GIA, we are poor.
I can't recommend the Mundelein Psalter highly enough. If you are dealing with a start-up situation, it fits the bill. "Obsolete"? Hmm. Maybe soon, but not yet.
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