As long-time readers of this forum know, I play more saxophone than bass or guitar, so I can't avoid commenting :-). In Peter's posted video, Randy Emerick is playing a contrabass sax. This is an octave below a baritone, which is the largest sax commonly seen.
Most modern baritones can sound the C below the E string on a four-string bass, or the first fret of the B string on a five-string bass. The contrabass is an octave below that.
The contrabass is, IMHO, only a novelty instrument. It's too big to transport easily; can only be played from a rigid stand; takes too much wind for legato passages. But it does make for a fun YouTube posting :-)!