Some keyboard pieces (the couple of five-part fugues from Bach's WTC, for example) require cramming five polyphonic voices onto just two staves. Usually this means three voices to either the upper or the lower staff. What could be some good typographical guidelines for engraving such music without things becoming extremely messy?
Two voices to a staff is relatively easy; you just flip the note stems for each voice consistently up or down. (Though this might messy too, if there's a lot of voice crossing.) But for three voices this doesn't seem really sufficient. I've seen a few scores where the note stems for the three voices aren't exactly lined up, but separated by a tiny amount of horizontal space. What are the typographical procedures for that? I'd be interested in hearing any other methods as well.