This is a major achievement! Congratulations!

...except those for the COMMUNIA and for a small number of errors in A&R. All other melodies have been transcribed from the medieval manuscripts resp. the printed editions as indicated in the OCO. A number of antiphons marked SOL i.e. "Composed by Solesmes" and apparently unpublished I have composed myself.

Did you indicate the various sources in your document?

Someone please edumacate me- what is this OCO?

@lmassery as you know, the Mass has one set of antiphons in the Missal, intended for said Masses (without music), but also an official set of Gregorian propers which do sometimes match, governed by the Ordo Cantus Missae and printed in the Graduale Romanum, Graduale Novum, Gregorian Missal, etc.

The situation with the Liturgy of the Hours is the same. The texts in the common 4-volume set of books are intended for recitation, but there is also an official corpus of Gregorian chants for singing the office, governed by the OCO, and until now, not available from any single source. The official OCO is written like a bibliography, pointing you to a bunch of different sources, many rare or out of print or unpublished. The Antiphonale Romanum and the other existing books for chanting the new Office cover some but not all of the Hours, so it is a truly arduous process to attempt to chant, say, the Office of Readings, involving a lot of hunting and gathering and often composing one’s own settings when nothing can be found.

So what Joerg has done is truly amazing – providing a single source for every antiphon one needs to chant any Office, any day of the year.

One thing which might improve this already Herculean achievement would be to include page numbers in the Index Antiphonarum and Index Responsorium Brevium, as there are already in the Index Hymnorum and Index Antiphonarum ad Invitatorium (although the page numbers given in those latter two indices refer to the Liber Hymnarius, and not to the OCO itself).

By omitting page numbers, you force the user to learn the logic by which the OCO is organized in order to find any particular antiphon. While that's a laudable goal, I think it will be frustrating for many users who wish to look up an antiphon without having (yet?) mastered the intricacies of navigating the entire volume. There is horizontal space for an additional column in those two indices, and I would urge the inclusion of the OCO's page numbers for ease of use.

(Now that the OCO document is otherwise complete, the page numbers shouldn't need to be altered; that is, there's little-to-no danger that two indices with page numbers would need to be updated at some future point to reflect changes in the page numbers.)

Ah — I see now! Optimized for viewing on a computer. I was thinking of the old-fashioned printed book, where page numbers are still essential. (They might yet be useful if anyone were ever to print-and-bind this volume into an actual physical book.)

PDFs should be made with printing in mind even if you think that people probably won't print it. You should also take advantage of technology when appropriate, such as links that activate for those using screen readers (i.e. the blind and visually impaired), but that shouldn't affect the final document.

I have uploaded indexes with page numbers for invitatories, antiphons and short responsories: oco_idx.pdf. (The pages with melodies are underlined.)
@smvanroode: My next step will be to add links to the sources, but it will probably take some time.