There are parishes where the pastor has said to the schola or choir: no Latin under any circumstances, not even for the propers that the schola aspires to sing. They can chafe and complain about this edict, or they can find a workaround, still using music of the Roman Rite while employing the vernacular.
Before very recently, this was a tricky proposition but in the last year or so, everything has changed. There are now fully six sets of English propers online.
One of the most distinctive projects is the American Gradual compiled with loving care by Bruce Ford. He has preserved the Gregorian melodies for all of the propers, and he has done this for good reason. These are the most wonderful melodies ever written. They are bound up with the history of the Roman Rite. They have inspired musical elaboration for many centuries. They capture the sense of the text in a beautiful way. Even in English, they are worthy of preservation.
It goes without saying that a critical part of the musical information is lost in translation. The words cannot match the melodies precisely. And English is an awkward language to set to melismatic chant, given the hard endings to words. But Ford overcomes the obvious limits with sensitivity to the text.
What I especially appreciate is how these are highly useful for some circumstances where the Latin propers are not possible, and yet their structure is always working to point to the ideal. So it can be a highly useful expenditure of any schola's time to sing these pieces as they prepare for the future. And in the meantime, they are providing a rooted experience in the actual melodies of the chant.
Let's consider the Offertory chant for the 4th week in Easter: Deus, Deus Meus. It has a contemplative and pleading quality to it. The song is about waiting in anticipation for the Lord, so we have the musical effects of repeated phrases, the daybreak, and hands being lifted up. It is all very rich material. The Gregorian setting is as follows:
And the English from the American Gradual is as follows:
You can see that the Do is not movable if you are going to stay within the written key, though there is nothing to prevent you from taking it up or down. And notes are more-or-less modern with a special adaption for plainsong. Otherwise, the same principles apply to this as would apply to the authentic Gregorian version: always legato, no breathing during words, crescendo through the pressus, etc.
Now, having gone through this chant and sung it this last weekend, I can't say that it is somehow easier than the Latin version. The greatest challenge is keeping a group together as they sing. The teaching must begin with a clear rhythmic sense. I started this as 120 bpm to the punctum and adjusted as the episemas and text demand.
The most important single principle here is not to rush or panic through phrases but rather take all the time you need and embrace the phrasing as the piece seems to demand. For example, following the phrase "I will lift" you need to close the T together and leave space before settling down on the E. Start slowly and calmly and the melody begins to take shape in a beautiful way.
Ford has put together the entire Graduale Romanum in this way, and is in the process of correcting his manuscript one season at a time and posting it as he completes the project.
There are many uses for this but the one that occurs to me most readily is the parish situation in which Latin is out of the question, and this is not an unusual case. Singing these provides exposure to the congregation and the schola of the authentic melody at a feel for the sensibility of the music. This project offers a vigorous challenge to the conventional view that the melody must be changed in light of the translation.