Thanks, Barbara. That's just how we're doing it, but I didn't realize I was singing the tenor part. We picked the key of Dm (rather than Am as written in the Southern Harmony) based on how low my husband could sing. He's normally a tenor, but I grabbed that part first, having found the song and learned that part previously. Then a soprano came along and had no trouble with the high part. The last guy to join our little ensemble ended up singing the tenor part with me but an octave lower, apparently just as the music was intended!

I'd be very interested to see a fourth part if you find one, but I'm wondering who would get "stuck" singing it. Probably that last guy to join us!