I'm pretty sure it's a larger version of a mandolin.

Vio-lin................Mando-lin Violon-cello (cello)...Mando-cello Bass...................Mando-bass

(I wonder if there's a Mandol-a , like a viol-a)

I just got an album at an outdoor concert in Salt Lake City where The guy was playing probably one of these It looked like a Mandolin twice as big as usual.

I'm sure someone else can give you more detailed information on this, though, this is just my best guess

rapunzel