Sub-Contrabass Clarinets  

There are two experimental instruments pitched one octave below the Contra-alto and Contrabass (the Octo-Contra-Alto and the Octo-Contrabass respectively).  They are curious might-have-beens, which extended the range of not only the clarinets, not only the woodwinds, but indeed the whole orchestra and band into a range never before used.  Alas, they never made it as usable instruments.

Prokofiev’s Humorous Scherzo for Contrabass and Octo-Contra-Alto Clarinet