I've found a external link for
ChoralWiki, home of the Choral Public Domain Library
However there is apparently no non-depreciated external relationship in which this link fits on the Work/Edit page.
I see that I can go a circular route and claim that this metadata is actually a lyrics page (It does have the lyrics too.) And link it to the recording. However that seems a very partial solution if there are many recordings of a work.
I do have some appreciation of the great benefits that keeping choices very tight has for the usability of MusicBrainz. And think that those responsible for that are doing well. But around Works I think that broader external links are needed.
Unless I am missing something (which is very possible)?