The reed is flat and the mouthpiece is curved backwards to allow of vibration. The reed is carefully thinned at the point where it vibrates against the curved table of the mouthpiece. The vibration is caused by the air pressure against the reed, thus engendering sound. The air-column in the instrument is shortened, or lengthened, by the opening, or closing, of the holes and keys, emitting high, or low, sounds accordingly. The reed vibrates through the action of the air. The lips of the player merely encompass the reed and mouthpiece, slightly pressing the reed. Again, to quote from Lavignac: “This instrument, the richest in compass and in variety of timbre of all the wind instruments, is subject to a very special and very curious law. Its tube is absolutely cylindrical and open; and its column of air is set in vibration by a single, flexible reed. Now a peculiarity in pipes of this construction is that the vibrating segment forms, not at the middle point, but at the end where the reed is, so the mode of subdivision of the air-column is the same as if the pipe were stopped. The clarinet has, therefore, only the harmonics of unequal numbers, which renders its fingering very different from that of the flute, the oboe and the bassoon. It would seem that this might place it below them. On the contrary, this instrument lends itself with admirable suppleness to the expression of all sentiments which the composer may wish to entrust to it. [Illustration: CLARINET, SYMPHONY SOCIETY OF NEW YORK _Gustav Langenus_] “Its compass, the greatest possessed by any wind-instrument chromatically, has a great deal to do with giving it this richness of expression; but the diversity of _timbre_ belonging to its lower, middle and higher registers must be regarded as the real superiority of the clarinet.”