ADJPAnderson,

Charles is right that the sections who need the most help should get it.

An important approach is to conduct entirely through one bar before any voice sings anything. (That is, when you've got actual singers in front of them and you risk keeping the impatient waiting, it's important to count one complete bar: this gives everyone a solid sense of the tempo of the piece, and allows those who aren't otherwise going to pay any attention to the conductor to know their marching orders.) I recommend subdividing beats early on, so that the first entrance and the second entrance don't come by surprise.

Sometimes a "cue" isn't more than looking at the section. Not everyone needs Leonard Bernstein's effusive cues.

conduct entirely through one bar before any voice sings anything

After sufficient yelling, you can get away with only an upbeat.

Tenors don't come to every rehearsal, do they?

Mine did. And in the church choir in which I sang for a few years, the tenors showed up for every rehearsal, too.

I've been told that it's harder to attract people of ANY voice to a church choir these days.....

Some more general guidance:

I advise preparation (and, in fact, personal performance) of the score as if it were a contrapuntal work for keyboard, if that is a familiar idiom to you. Identify related motives (often made easier by textual similarities as well as musical ones) and ensure they are shaped the same way. If your singers are not particularly individualistic musicians, working through phrasing and shaping on a part-by-part basis and marking that interpretation in a communal score is a great time-saver. Much of this is fairly trivial to devise once you know the idiom and have sung through each part a couple times - you want to preserve a sense of "inertia" that does not always arise from individual vocal technique. (This is a difficult concept to explain textually.) The individual dynamic flow of each line, rather than dynamics shared among the entire group, is what gives Renaissance polyphony its distinct character, with notably few exceptions; achieving this in a larger group is difficult but manageable.

The other reason I advise arriving at your interpretation ahead of time is that this music is notoriously difficult to rehearse interpretatively. Each part is almost completely independent and much of the rehearsal toolbox becomes useless because of it. The interpretative impetus needs to come from the singer/section on each part and there is much less that the conductor can do to incite that without making the music too homogeneous. With more independent singers, this becomes both much easier and much harder, depending on how willing they are to listen to one another.

Don't be afraid to take liberties with the interpretation depending on the verbal text. The worst interpretations of polyphony are those that all sound the same regardless of the textual content, and some of the best take rather stunning risks (see: Christophers/The Sixteen, Victoria Tenebrae Responsories). Though such gradations are too subtle by our standards to have been marked by the composer, they are an essential part of the music. Do remember to keep such interpretation polyphonic rather than homophonic, of course.

Vocal notes: tenors need true head register development to manage the tessitura in these works, and falsetto is a more appropriate tone than belting for most of them that won't have the private vocal development necessary to achieve that. Make sure your singers are singing "on the voice" or much of the shaping and "inertia" won't happen properly. Singing "on the voice" at high dynamic levels devoid of vibrato seems to be incredibly difficult and/or unintuitive for some people, but I've never found it a particular challenge, so I don't have much in the way of advice on that.

It might be useful to remember you're not cueing entrances as much as breaths, and for that you don't even need hands. I remember feeling a bit humbled in an early part of my career when a bell choir played exactly as well when I literally had my hands full subbing for a missing member: a breath was all it took to start together and my eyes could do the rest. And starting with a single preparation is an essential skill; bars for nothing just make people nervous.

That's a matter of rehearsal and performance technique rather than something that requires that technical choice, Chris. It risks becoming a crutch.

Another consideration: if you habitually cue all parts (sometimes, but not often necessary), people will expect that. When you get them into harder pieces of music, it will be both difficult to cue all parts AND difficult for them to follow.

Assuming the piece is metrical, it's important to make sure there is a sense of pulse (or tactus, if we want to talk polyphony). You have to show that, but more importantly, the choir has to FEEL that. So, a lot of the "pressure" is really on them to get to know the music.

We had a little issue with the Victoria Ascendens Christus because a couple singers honestly didn't practice the music in such a way that they understand how their notes work with the tactus. That's a big issue! I can conduct the piece (well) as much as I want, but I couldn't help them because...they just didn't know it.

I think it's fine to say to a section, "You'll need to know this release since I have to cue the altos" or vice versa. Ditto, if a section is particularly tricky and the singers in a section are having trouble, you should just say, "watch me, and let me make the mistake!" (assuming that you won't!)

Schoenbergian,

It's the teacher in me.... sorry. I see it as scaffolding to teach groups to sing well, to help them gain confidence. It also helps focus directorial attention (since I've seen a piece directed accidentally in 2 when the director forgot to shift speed as he shifted to minims from crotchets). Imagine Sicut Cervus as sung by the Chipmunks. Fortunately, the piece didn't get very far, and it was a rehearsal. Yes, you're quite right that it could become a crutch, preventing development in a single individual, a part or an entire ensemble.