The contrast in texture between the single melodic line of plainchant and the lushly interwoven but independent melodies of polyphony is no doubt a useful one. What’s their full dramatic potential? Abundance in polyphony, simplicity in plainchant, forceful articulation in homophonic harmony, silence: each has its place in the weekly and yearly cycle of divine service, as public worship has many parts and various seasons.
But in writing music we aim either to intensify the sense of the text or to problematize it with irony that emerges from the context, not to put out ostentatious displays. There can be more stately restraint in six-part polyphony than in an overly showy homophonic setting that attempts to mechanically inject something interesting. A lot of music, Baroque and onward, is too theatrical for the church and belongs to the concert hall.
Spectacle is not for liturgy and thus must be kept out, much as Finneyism is to be kept out, but dramatic power and mystical intensity in musical delivery of holy texts can be used to draw the heart of the worshipper into the sublime mysteries of the faith which are the logic of Scripture. A well-placed dissonance can express the heartfelt depth of the Church’s plea before God; the dark colour of parts on a lower register (e.g. multiple bass parts) can express the solemnity of feast or of mourning; soaring discants can acknowledge heaven piercing the earth.
But first evangelism, then glory. One problem with the multiplicity of churches is that churches look rather to the increase of numbers than to the numbers that they know they must serve, and then they aim all to act as if they have the resources of a diocesan cathedral. This, too, calls for restraint: as the gospel’s preached and the nations all come to believe, glory will indeed increase into glory, but we see present reality as well as future reality that we know by faith.