Back in the 1990's I was asked to write an arrangement of the hymn "Come, Thou Fount of Every Blessing" for choir SATB and piano. Since then, every time I've revisited it, I've rewritten it.
Most recently I was looking at a perpetually troublesome section and trying to improve it. In the process I discovered some undesirable parallel perfect intervals. If I tried to eliminate parallel perfect 5ths, I ended up with parallel perfect octaves nearby.
I finally realized that I could eliminate them by reverting to the original voice leading of the hymn, which was written in the key of E-flat. In previous versions of my arrangement, I had written the first verse in E-flat, then modulated to F major for the second verse. The voice leading problems had occurred as I tried to avoid having the tenors sing uncomfortably high notes (a whole step higher than in the original hymn).
I still wanted to have a modulation from a lower to a higher key between verses. If I moved everything down a whole step, the first verse would end up in D-flat major. I decided against that. Previous arrangements had appealed to beginning choirs because it was fairly easy for piano accompanists. I would hate to make them play in 5 flats (although I'm quite happy myself with that key.)
With that in mind, I decided to begin in D major and modulate up a half step to E-flat major for the second verse, which would then end in the same key as the original hymn.
Having played the original modulation so many times, it was hard to replace the whole-step modulation with a half-step one.
I finally settled upon using a modification of the "resolving-a-dominant-7-chord-as-a-German-6-chord" trick. (In this case, instead of a dominant [major-minor] 7 chord, I used a minor-minor 7 [vi7 to be exact] as the pivot chord.)
You can see what I came up with at https://weldonwhipple.org/music/comethoufount-2020.pdf. I hope you like it.