I'm curious.... the round symbol on these pages as well in pics of the group ... is there anything symbolic about it? How did this symbol come about?
Excellent question, Greg. I went and looked at my CD collection and I believe the symbol was first used on Masters of Chant Chapter IV.
I'm not sure who designed it but I think everyone thinks of it as the "tribal" symbol. It's used frequently in artwork and tour merchandise now and has also become a popular "tattoo" artwork amongst the Gregorian fans.
It's similar in composition to a celtic concentric circle, though less detailed. If you want a prime example of such things, look up the Book of Kells, which contains a stunning Eighth Century example of Irish illuminated manuscript. Illuminated manuscripts tend to use many such concentric circles.