The Daily Devotion I had today was singing as worship, which reminded me of Christian music resources we may have in the library.
Three reference books in this area, only one current, could be useful for aspiring church choir conductors and musicians.
McCutchan's Hymn Tune Names: Their Sources and Significance (1957) deals with the names of tunes which if you know, you are liberated in singing and playing without music. My sister-in-law had to memorize them when she was studying to be a church musician. How many hear this without thinking of a major disaster? Another tune was also called this originally but renamed to Crucifer because it is always sung with these lyrics
Another more recent work is Powell's Encyclopedia of Contemporary Christian Music (2002) and is more a biography of Contemporary artists and groups. It looks like a fun browse with some "remember when" displays.
Although larger in scope than church music Unger's Historical Dictionary of Choral Music (2010) also focuses on composers and lyricists and choral music terms. I looked up John Rutter who's Gaelic Blessing is one of my favorites although I never sang it in a choir. There is also an extensive bibliography of secondary sources for many of the major composers. At this point, I wish this were online even if students were to ask "Where's the full text? or Is that all there is?"
On this point, I leave with the One word chapter another writer gave about Singing in church.