Below is a response from Rev. Jesse Krusemark of Trinity, Waltham and St. Paul's, Hollandale, Minnesota to a request for choir resources connected to the Historic Lectionary:

“First I would recommend a couple Facebook groups 1) The One-ders: One Year Lectionarians and 2) The Wondrous Musicians of the One-Year Lectionary Congregations. It would be especially in the second group that you could bring forward the questions you have regarding well-ordered church music for your active choir. Your lead musicians could also join this group themselves. I know that several of the contributors there do have lists they’ve compiled of choral resources for each Sunday and feast, especially Christina Joy Roberts of Grand Rapids, Michigan and Gary Schultz of Terra Haute, Indiana. Another good resource for you would be Tom Lock, active in these groups. He produces choir music for the one-year lectionary through his publishing company Salpidzo Press. 

A great place for your choir to begin would be with the introits and the intervenient chants, which along with the collects often contribute as much to the character of the Sunday or feast as the lectionary texts themselves. CPH offers a couple of collections, that of Healey Willan, The Introits and Graduals for the Church Year and Paul Bunjes, The Service Propers Noted. From Lulu Press can be gotten The Lutheran Propers compiled by Fritz Eckardt which includes the settings of those same chants by Walter Buszin. Something more up to date of the same type is the Acclamation series from CPH, available for both lectionaries and downloadable (some of the Advent 1 Year ones seem to be free right now). liturgysolutions.com also produced more contemporary settings of these chants for both lectionaries, but it seems to be currently defunct. For challenging Gregorian settings preserved in Lutheran use, see The Lutheran Gradual of Matthew Carver (Lulu Press).

The next thing for the choir would be to highlight the Hymn of the Day, a de facto proper, with the elaboration of one or more stanzas or by an antiphonal presentation. Daniel Reuning (included on Pr. Petersen’s reply) has made simple two-part settings, the cantus (women) with a single counterpointing line (men). They’ve been in regular use at Redeemer, Fort Wayne, Indiana for years. Due to copyrights and the distraction of other publishing projects we’ve not succeeded in making these widely available. But an able musician in your midst could produce something very similar without much trouble. Such could be done by adapting the soprano and bass lines from Bach’s setting of the chorale. Or your choir could sing Bach’s full setting in four parts or other settings which differ from that sung by the congregation. Ralph Gehrke in Planning the Service gives a lot of suggestions for antiphonal renderings of hymns. My copy of this resource is a reprint from Concordia Theological Seminary Press, Fort Wayne, Indiana. It might still be available, else you could beg and plead a photocopy in one of the Facebook groups above.

Hymn associations with Sundays and feasts go beyond the Hymn of the Day. Gehrke (cited above) for example gives other hymn suggestions. I’ve made something of a collection of hymn lists, some quite old, so I could see what Lutherans have been singing across time. This project was spurred on by the recent availability of our first synod hymnal in English translation, Walther’s Hymnal, CPH, 2012. Matthew Carver was the compiler and contributed many new translations to the volume. He also maintains a blog, Hymnoglypt with many treasures.

Sadly, many hymns considered standard board for Lutherans in their first 200 years, though mostly maintained (at least in our circles) while we yet spoke German, were precipitously dropped in the transition to English. So, for instance, if one should wish to look at a Bach cantata for inspiration for preaching or service planning, the chorale may or may not be familiar but more of these (and more of their stanzas) are now accessible in a singable form in English thanks to Carver. All this is noted in my collection. I’ve more lists that I’ve not yet included in the collection, but here’s the link to the resource which will remain live even as I update the file: https://www.dropbox.com/s/ff4xfuv09jnxwwx/Hymns%20ABC.pdf?dl=0 Scroll to the last page of the document for an explanation of each list included. Here’s another worthy hymn guide from Ron Stephens: https://www.dropbox.com/s/j53wzrpglba8wth/Stephens%20Hymn%20Guide.pdf?dl=0

Of course, once one’s got a hymn, he can search for settings in all the regular places one hunts for choir and organ music, including http://www3.cpdl.org/wiki/index.php/Main_Page and http://imslp.org/wiki/Main_Page for online freebies. Your choir might enjoy working through something like Distler’s Der Jahrkreis, part of which is available in translation from CPH. But there are others who could better guide you through the available literature. I’ve only an occasional choir employed at Christmas and Easter capable mostly of unison singing. We’ve made use of Matthew Carver’s Liber Hymnorum (Emmanuel Press) to sample of Lutheran Latin hymnody. This would be great for a choir for prayer offices. I know Mr. Carver’s due to put out a volume of sequences at some point which should also prove worthwhile.