Triple contra bass viol?
Nope, it's an Octobass. (Notice it only has 3 strings, (and is a full octave below a double bass)) There was also another very short lived giant bass instrument that once existed w/o the mechanical levers w/ 4 strings that had to be played by two people, one bowing at ground level, and another fingering the notes while standing on a raised platform.Triple contra bass viol?