This is the lowest clarinet to be found today sounding one octave below the Bass Clarinet. It is always pitched in B-flat (contrary to what Arnold Schoenberg wrote in his 5 Orchestral Pieces when he scored for an instrument in A!). All student instruments possess the written low E-flat, while all professional instruments are constructed to low C.
When we picture a “contra clarinet,” it is the B-flat instrument that we think of not the smaller E-flat Contra-Alto. Were I forced to choose between the two instruments, I would almost always pick the Contrabass against the views of the players. Here’s why: when doubling the Bass Clarinet at the octave (which is the primary job of the contras), I don’t want to suddenly have to have the two instruments in a unison because the smaller Contra-Alto cannot reach the bottom notes. This octave doubling is the mainstay of writing for the contra clarinets. It is completely akin to the Basses and Cellos in the orchestra. The Basses almost always double the Cellos down one octave. Of course the Basses have the same problem as the Contra-Alto Clarinet if they do not possess a low C extension, for they will not be able to double the octave of notes below their low E.
This said I would rather have both instruments. They can play in unison, or octaves, or even harmonies. When I have heard a single Contrabass added to a standard sized band, I have felt that it has made very little difference to the overall sound. It should have been much greater. The problem occurred in that there were too many higher clarinets which overpowered the lower ones.
A great comparison should be made between the Contrabass Clarinet and the Contrabassoon, our lone members of the true bass in the woodwind section. Like all clarinets, the Contrabass is capable of infinite softness, whereas the Contrabassoon cannot do this. The Contrabass Clarinet is also capable of hiding in nearly any texture simply adding its soft voice. The Contrabassoon adds a more distinctive and richer voice. Together (with the Contra-Alto) they can provide a warm bass able to supports the winds.
The upper register of the Contrabass is thin and strained and best avoided. Some instruments may not have the full complement of trill and alternative keys so the upper range is limited in that regard as well. But this raises the question, why are you writing in the altissimo register for the Contrabass Clarinet anyway?
Please include this instrument in your writing. Just as the strings are incomplete without the Basses, so too are the woodwinds incomplete without the contras.
Himno al Sol for Contrabass Clarinet, Cello, and Piano
(This is quite possibly the best video of any of the Contra Clarinets that exists)
Fucik’s Der Alte Brummbär