This instrument has been making a revival over the past few years. It is the only clarinet that does not transpose. It is typically grouped along with the B-flat and A instruments as a “soprano” clarinet. In fact, the C Clarinet uses the exact same mouthpiece as does the B-flat or A. Mozart, Beethoven, and Schubert all used the C, though this may have just been out of convenience of key (though I doubt this as the sound of the C Clarinet in nearly all cases makes a huge improvement). It all but disappeared during the Nineteenth Century until Mahler and Strauss rediscovered the unique sound of the instrument. In their works, it became a member of the higher clarinets (grouped more with the E-flat and D instruments). So we can see that the C Clarinet is a sort of chameleon that bridges the gap between the sopranino clarinets and the soprano clarinets.
At one time, I owned a C Clarinet to experiment with the different timbral possibilities of this unusual instrument. I was struck with how different it sounded from the standard B-flat. I would say that the C Clarinet is by far the “happiest” of all the clarinets. It is chipper and even fun at times. In playing Mozart’s Cosi fan Tutte, I was privileged to sit next to a clarinetist who played several of the arias on my C instrument. She had started out using a B-flat or A to play those parts, but when the C became available, the sound change was apparent to the entire woodwind section. Just the slight change to a smaller instrument changed the entire character of the whole woodwind section. I think Mozart knew quite well what he was doing in scoring for the C.
To my knowledge, the C Clarinet has never been featured in the band outside of a few early Nineteenth Century scores (e.g. Mendelssohn’s Trauermarsch). There is no reason for it not to be included. The C Clarinet that I purchased was fairly inexpensive and played quite well such that any group should be able to afford one.
It would make for an interesting timbral change from the standard B-flat sound, and could serve as an upper voice in clarinet choirs. I feel that at least one should be available to all bands above a certain level. Certainly college level groups should have at least one (preferably two) available for use. Why not include it in works for band?
Bach on C Clarinet
Handel on on C Clarinet