Hi, Kicky - it doesn't take many people to make a good song circle, If you can get a core group of four people, you've got a good start. Our Sacramento circle has some 40 people each time - it's fun, but sometimes unwieldy. I also belong to one in the Gold Rush town of Auburn, and that one often has as few as 8 people - and the singing can be wonderful.
Heck, my friend Claudia and I can sing the night away, just the two of us. We find, though, that we don't sing very often when we're all alone. We can play an instrument by ourselves for hours on end, but singing seems to have a social aspect that playing an instrument doesn't have.
-Joe Offer-