I'm sitting here listening to the three-female group 'Grace Notes', (who you may not know, Jerry) and thinking how incredibly effective it is when they drop into unison, although most of what they sing is in three-part harmony. But maybe part of what makes it interesting is the different tones of the voices rather than the different notes.

Whether people are singing the same note or note is likely to depend on how many are in the group. If you've only got three, then it's possible for each one to always be singing a different note, but if there are more, then it's almost impossible unless it's a very complicated chord (and that would sound very strange if each chord was a fancy one), or they are singing in a different octave, when it becomes more a matter of tone - and the more people there are, the harder it becomes. Having said all that, I think it can be very effective, even with just two of you, to occasionally drop into unison for a few notes (just listen to early Watersons).

Just thinking aloud - hope it makes sense!

Barbara