When writing a choral arrangement, variety is more complicated than complexity. That variety encompasses not just melody and harmony, but also voicing and timbre.
As an exercise for a recent conference presentation, I decided to take a simple melody (Mary Had a Little Lamb) and come up with as many ways to harmonize it as I could (without changing the chords). I came up with 28 different ways, but I’m sure there are more.
Feel free to use this handout as an exercise in your arranging lessons, or as inspiration for your own writing.