This name of clarinet, or clarionet, became accepted for the entire instrument, including the chalumeau register.  It is the communication between the external air and the upper part of the air column in the instrument which, initiating a ventral segment or loop of vibration, forces the air column to divide for the next possible partial, the twelfth, that Denner has the merit of having made practicable.  At the same time the manipulation of it presents a difficulty in learning the instrument.  It is in the nature of things that there should be a difference of tone quality between the lower and upper registers thus obtained; and that the highest fundamental notes, G sharp, A and B flat, should be colorless compared with the first notes of the overblown series.  This is a difficulty the player has to contend with, as well as the complexity of fingering, due to there being no less than eighteen sound holes.  Much has been done to graft Boehm’s system of fingering upon the clarinet, but the thirteen key system, invented early in this century by Iwan Muller, is still most employed.  The increased complication of mechanism is against a change, and there is even a stronger reason, which I cannot do better than translate, in the appropriate words of M. Lavoix fils, the author of a well-known and admirable work upon instrumentation: 

“Many things have still to be done, but inventors must not lose the point in view, that no tone quality is more necessary to the composer than that of the clarinet in its full extent; that it is very necessary especially to avoid melting together the two registers of chalumeau and clarinet, so distinct from each other.  If absolute justness for these instruments is to be acquired at the price of those inestimable qualities, it would be better a hundred times to leave it to virtuosi, thanks to their ability, to palliate the defects of their instrument, rather than sacrifice one of the most beautiful and intensely colored voices of our orchestra.”

There are several clarinets of various pitches, and formerly more than are used now, owing to the difficulty of playing except in handy keys.  In the modern orchestra the A and B flat clarinets are the most used; in the military band, B flat and E flat.  The C clarinet is not much used now.  All differ in tone and quality; the A one is softer than the B flat; the C is shrill.  The B flat is the virtuoso instrument.  In military bands the clarinet takes the place which would be that of the violin in the orchestra, but the tone of it is always characteristically different.  Although introduced in the time of Handel and Bach those composers made no use of it.  With Mozart it first became a leading orchestral instrument.