Page:EB1911 - Volume 13.djvu/716

 All the crooks, a list of the principal of which is appended, therefore necessarily give real sounds lower than the above series according to their individual length.

Table of Principal Crooks now in Use.

The practical aggregate compass of the natural horns from B♭ basso at the service of composers therefore ranges (actual sounds) from or with 3 valves from By means of hand-stopping, i.e. the practice of thrusting the hand into the bell in order to lower the sound by a tone or a semitone, or by the adaptation of valves to the horn, this compass may be rendered chromatic almost throughout the range.

The principle of the valve as applied to wind instruments differs entirely from that of keys. The latter necessitate lateral holes bored through the tube, and when the keys are raised the vibrating column of air within the tube and the ambient air without are set in communication, with the result that the vibrating column is shortened and the pitch of the note raised. The valve system consists of valves or pistons attached to additional lengths of tubing, the effect of which is invariably to lower the pitch, except in the case of valve systems specified as “ascending” tried by John Shaw and Adolphe Sax. Insuperable practical difficulties led to the abandonment of these systems, which in any case were the exception and not the rule. The valves, placed upon the U-shaped slides in the centre of the horn, are worked by means of pistons or levers, opening or closing the wind-ways at will, so that when they are in operation the vibrating column of air no longer takes its normal course along the main tube and directly through the slides, but makes a détour through the extra length of tubing before completing its course. Thus the valves, unlike the keys, do not open any communication with the ambient air. Even authoritative writers have confused the two principles, believing them to be one and the same.

French horns are made with either two or three valves. To the first valve is attached sufficient length of tubing to lower the pitch of the instrument a tone, so that any note played upon the horn in F while the first valve is depressed takes effect a tone lower, or as though the horn were in E♭. The second valve opens a passage into a shorter length of tubing sufficient to lower the pitch of the instrument a semitone, as though the instrument were for the time being in E. The third valve similarly lowers the pitch a tone and a half. It will thus be seen that the principle applied in the crook and the valve is in the main the same, but the practical value of the valve is immeasurably superior. Thanks to the valve system the performer is able to have the extra lengths of tubing necessary to give the horn a chromatic compass permanently incorporated with the instrument, and at will to connect one or a combination of these lengths with the main tube of the instrument during any interval of time, however short. The three devices, crooks, valves and slides, are in fact all based upon the same principle, that of providing additional length of tubing in order to deepen the pitch of the whole instrument at will and to transpose it into a different key. Valves and slides, being instantaneous in operation, give to the instrument a chromatic compass, whereas crooks merely enable the performer to play in many keys upon one instrument instead of requiring a different instrument for each key. The slide is the oldest of these devices, and probably suggested the crook as a substitute on instruments of conical bore such as the horn.

The invention of the valve, although a substantial improvement,