About backing vs singing lead. I agree completely that it's at least as much fun to harmonize as to sing lead. It's a skill in itself to be able to throw in a harmony that fits the song without trampling on the melody--just being part of the musical texture is immensely satisfying--and I love to do it. Jan calls me a harmony slut--I'll sing with anybody who likes it--duets, trios, quartets, bigger groups.

And it's also what I try to do with the viola--just compliment the melody--which it seems is much easier to do with a low harmony than a high one--so the viola works well. It's great fun to try to guess where the melody is going if you've never heard it before. And you have to recognize if the melody is more complicated than you first thought--and to just listen til you know you really have it. But it is great fun--and amazingly well appreciated.

If somebody is singing a cappella the chances are he or she wants to be free to lengthen or shorten the notes and phrases in telling the story--and you have to wait for a chorus or refrain before putting in a harmony. At least that's what I've found--and I have to admit that, sure enough, in the verses if I'm leading the song, I like to be able to be free in phrasing. Unless of course the song is an anthem--like John Tams' Rolling Home for instance, where the driving rhythm is important, even though the song is unaccompanied.

It seems to me that either you need to know in advance how the person is going to sing the song or there needs to be a very steady rhythm, often from a guitar--otherwise making up a harmony is really hard--and may even detract from a song.

But there are certain rough-hewn genres where there's more give and take--like sea chanteys.

It seems there's a whole science of harmonizing.