Here is an interesting find: Pange Lingua (1916): Breviary Hymns of Old Uses, with an English Rendering. Some I recognize but most I do not. There is no musical notation but that should be easy enough to find. The main use is probably for program notes for the congregation. But the main (to my mind) value of this short book is the remarkable introduction by Adrian Fortescue, which covers the whole history of Christian hymnody in about 30 pages. Talk about lost scholarship!
The hymns are given first in Latin and an English translation follows. I'm sure it would be easy to find - or write! - a hymn tune to match the rhythm and content of the words in each case.
The table of contents introduces the particular use in the church calendar for each hymn, and it also gives the hymn's origin; this is just what I've been looking for, really, except I was hoping for some musical notation as well. I wonder whether there would be some way to find out what the tunes were? I'd love to research this.
Again, I warn that this is a big file: 122 pages. It's a wonderful find, though! Hymnody is the one particular weakness of most Office books, and yet it's something very basic to worship. We also ought to start contributing new hymns to the mix.