the jugband spoke
Yes, the jugband spoke. all male members of the jugband had lines. I think Lou migth have had an off-camera line. When Lobbock Lou sings, it's a close-up shot of him, and we briefly hear a voice that says "crystal clear!" which sounds like either a dave goelz or steve whitmire voice (i can't tell which one it is, but since louise gold didn't perform in the special she obviously couldn't have voiced her). All of the other members spoke, and her seen, so it couldn't have been any of the others.
I know you didn't ask, but in case you are wondering, dave Goelz performed Lobbock Lou, Jerry nelson performed jerry, Jim henson performed zeke, richard hunt performed bubba, and frank oz performed gramps (in other words, all regular performers except for whoever performed lou. they have occassionally been voiced by other performers).
They sang a song called "take it away".
If you need to know which bear was in it, it was the bear who appeared in Lullaby of broadway (in the gilda radner episode) and at the end of the marty Feldman episode. I can't remember if this bear is brown or gray.