A huge part of what makes organ’s sound the way they do is that you stack up different ranks of pipes which play at different octaves.
Here is a crude, quick overview:
Each rank of pipes has a number that tells you what octave (typically) it is. If something is marked 8 (or 8 foot) that means if you play a middle C you get a middle C. If something is marked 4, you play that same key and get a note an octave up. If it’s a 2, that’s higher another octave, and sometimes you get 1’s, which are really high. In the other direction you get 16’s, which play an octave lower than the 8 would, and these are very common in organ pedals. Then sometimes you get 32’s, with big organs, and those are down yet another octave. Those are the pipes that rumble. I’ve heard rumors of 64’s but I have never met one.
There is more to it than that but the idea is that you play one key on the organ and can get a host of pipes and octaves playing at the same time. This makes the organ have a richer sound, when you want it (using just one rank for a solo is also very common) and this controls how loud the sound is going to be. More pipes – more sound. ANd if you use all the ranks of pipes you have, that’s called full organ and it’s immense. SO loud in fact that organists frequently loose or damage their hearing because of how loud it is. (Someone should put some thought into this when building organs.)
Going back to my piece, I’m now using some of the same melodic material from yesterday but I’m doubling octaves all over the place, sort of like using more organ ranks, such that I guide with a tune but whenever we are on a chord (as opposed to passing through notes to get to a chord) all the notes in that cord are there. I don’t mean all the pitches, I mean every note. So if you have a C major chord spanning two octaves it is C E G C E G C with no gaps. This makes a very rich sound, it’s something that I personally have no recollection of hearing a choir piece do in any sustained way, and since the actual chords themselves aren’t bazaar, it’s not that hard to do.
I used this idea in Be Still on the second reiteration of the text at the beginning for about one measure. So now I’m taking that idea from the one measure and building a piece out of it. It’s not a common texture for some reason, at least in choral music.
One thing is that this piece would be hard to do with a small choir because it’s constantly dividing in 6-8 notes. You need to have enough singers to cover all those divisi (splits) and the smaller the group, the more advanced the singers have to be. You could do it with 16 but they would all have to be fantastic.