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.
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.”
Berlioz says: “The clarinet is little appropriate to the Idyl. It is an epic instrument, like horns, trumpets and trombones. The voice is like that of heroic love. This beautiful soprano instrument, so ringing, so rich in penetrating accents, when employed in masses, gains, when employed as a solo instrument, in delicacy, evanescent shadowings and mysterious tenderness what it loses in force and powerful brilliancy. Nothing so virginal, so pure as the tint imparted to certain melodies by the tone of a clarinet, played in the medium by a skilful performer. It is the one of all the wind instruments which can best breathe forth, swell, diminish and die away. Thence the precious faculty of producing distance, echo, the echo of echo, and a twilight sound. What more admirable example could I quote of the application of some of these shadowings than the dreamy phrase of the clarinet accompanied by a tremolo of stringed instruments in the midst of the Allegro of the Overture to Freischütz! Does it not depict the lonely maiden, the forester’s fair betrothed, who, raising her eyes to heaven, mingles her tender lament with the noise of the dark woods agitated by the storm? O Weber! Beethoven, bearing in mind the melancholy and noble character of the melody in A-major of the immortal Andante in his Seventh Symphony, and in order the better to render all that this phrase contains at the same time of passionate regret, has not failed to consign it to the medium of the clarinet. Gluck, for the ritornello of Alceste’s air, ‘Ah, malgré moi,’ had at first written it for the flute; but perceiving that the quality of tone of this instrument was too weak and lacked the nobility necessary to the delivery of a theme imbued with so much desolation and mournful grandeur, gave it to the clarinet.
“Neither Sacchini, nor Gluck, nor any of the great masters of that time availed themselves of the low notes of the instrument. I cannot guess the reason. Mozart appears to be the first who brought them into use for accompaniments of a serious character, such as that of the trio of masks in Don Giovanni. It was reserved for Weber to discover all that there is of the terrible in the quality of tone of these low sounds.”
Mozart was the first to appreciate the beauties and capabilities of the clarinet. He wrote a Concerto for it with orchestra[24] and his Symphony in E-flat is so full of prominent work for it that it is often called the “Clarinet Symphony.” Beethoven loved it also and developed music for it far beyond Mozart’s ideas. It sings particularly lovely melodies in the Larghetto of the Second Symphony. In the Pastoral Symphony, where the flute sings the nightingale and the oboe pipes for the quail, the clarinet gives the cuckoo’s notes, or, rather, two clarinets together say “cuckoo, cuckoo.”