The cult of the soloist
ISTM that there are three kinds of liturgical vocal music: congregational, ministerial, and presidential. The first and last categories are, ideally, characterized by easy melodies conducive to singing by non-specialists. The other kind, ministerial, is harder music that needs someone with more developed singing faculties - or that requires dedicated rehearsal outside of the liturgy.
I can’t recall if I have blogged about this before, but the role of soloists seems to be something of a question mark running through (what I know of) Western liturgical tradition. I believe a consensus is that graduals and Alleluias were often historically sung with soloists on verses, and particularly pieces like the great “Qui habitat” and “Deus, Deus meus” tracts seem more soloistic in nature than not.
We have an abundance now of music that is not well-written for its ostensible purpose of conducing congregational singing. Tom Booth’s “Find Us Ready” is a good example of what I mean. The refrain learns easily enough, but to me, it still bears stylistic traits of solo singing: syncopation and “stop-go phrasing” (e.g. 2-3 quick notes, then 3 beats of rest, then a few quick notes, then rests, ...).
Assuming that one accepts my idea that “Find Us Ready” & Co., aside from any musical judgement, are best considered “soloistic” music, we are basically left comparing such melodies to the melismatic chants of the Proper, in that each kind of melody is best sung by a soloist.
And, in my opinion, there is very little that truly gratifies a choir in singing “Find Us Ready” in a chorale harmonization. (For an explanation, review my post about choral harmonies to congregational music.)