Part 19 (1/2)

VARIETIES OF STOPS

We have already remarked that the quality of a stop depends on the shape and construction of the pipe Soular, others circular Some have parallel sides, others taper or expand towards the top Some are open, others stopped

The two an pipes may be divided are:--(1) _Flue_ pipes, in which the wind is directed against a lip, as in Fig

138 (2) _Reed_ pipes--that is, pipes used in co air into the botto_ reed, such as is found in the ordinary ue when at rest stands a very short distance away froh the reed the tongue is sucked against the reed, blocks the current, and springs away again A _free_ reed has a tongue which vibrates in a slot without actually touching the sides Haran the reed adth to sympathize with the rate of the puffs of air which the reed passes Reed pipes expand towards the top

TUNING PIPES AND REEDS

[Illustration: FIG 144--A reed pipe]

Pipes are tuned by adjusting their length The plug at the top of a stopped pipe is pulled out or pushed in a trifle to flatten or sharpen the note respectively An open pipe, if large, has a tongue cut in the side at the top, which can be pressed inwards or outwards for the purpose of correcting the tone S the tops inwards with a uisher placed over the top and tapped; and sharpened by having the top splayed by a cone pushed in point doards Reeds of the striking variety (see Fig 144) have a tuning-wire pressing on the tongue near the fixed end The end of this wire projects through the casing By ue is adjusted to correctness

BELLOWS

Different stops require different wind-pressures, ranging fro the heaviest pressures

There must therefore be as many sets of bellows and wind-chests as there are different pressures wanted A very large organ consumes immense quantities of air when all the stops are out, and the puine Every bellows has a reservoir (see Fig 143) above it The top of this is weighted to give the pressure required A valve in the top opens automatically as soon as the reservoir has expanded to a certain fixed li the leather sides

[Illustration: FIG 145--The keyboard and part of the pneuan C, coroups of stops; P (at botto compressed air; M, manuals (4); S S, stops]

ELECTRIC AND PNEUMATIC ACTIONS

We have nal signals and points by the employment of electric and pneuanists The touch of the keys has been greatly lightened bythe keys open air-valves or complete electric circuits which actuate thedown the pallets The stops, pedals, and couplers also employ ”power” Not only are the performer's muscles spared a lot of heavy hen compressed air and electricity aid him, but he is able to have the _console_, or keyboard, far away fro with the singers, or in any desirable part of the choir or chancel, would be able to coan situated afar at the western end of the nave; would draw each stop in co their office;and-- the swell pedal in his ordinary manner, would obtain crescendo and diminuendo with a more perfect effect than by the old way”[31]

In cathedrals it is no unco for the different sound-boards to be placed in positions far apart, so that to the uninitiated there ans scattered about Yet all are absolutely under the control of aaway from them all, but connected with thean in the world is that in the Town Hall, Sydney It has a hundred and twenty-six speaking stops, five manuals, fourteen couplers, and forty-six coe from the enormous 64-foot contra-troan occupies a space 85 feet long and 26 feet deep

HUMAN REEDS

The most wonderful of all musical reeds is found in the human throat, in the anatomical part called the _larynx_, situated at the top of the _trachea_, or windpipe

Slip a piece of rubber tubing over the end of a pipe, allowing an inch or so to project Take the free part of the tube by two opposite points between the first fingers and thuht No through it The wind, forcing its way between the two rubber edges, causes them and the air inside the tube to vibrate, and a her is the note

The larynx works on this principle The windpipe takes the place of the glass pipe; the two vocal cords represent the rubber edges; and the _arytenoid muscles_ stand instead of the hands When contracted, these es of the cords nearer to one another, stretch the cords, and shorten the cords A person gifted with a ”very good ear”

can, it has been calculated, adjust the length of the vocal cords to 1/17000th of an inch!

Simultaneously with the adjustth of the windpipe, so that the coluth to vibrate in unison Here again is seen a wonderful provision of nature

The resonance of thethe shape of the mouth the various harmonics of any fundamental note produced by the larynx are rendered proet the different vocal sounds Helmholtz has shown that the fundamental tone of any note is represented by the sound _oo_ If theout the octave of the funda the second har the second and fourth harmonics; while for _ah_ the fifth and seventh must be prominent

When histle we transform the lips into a reed and the mouth into a pipe The tension of the lips and the shape of the mouth cavity decide the note The lips are also used as a reed for blowing the flute, piccolo, and all the brass band instru a coach-horn the various har the lip tension and the wind pressure A cornet is practically a coach-horn rolled up into a convenient shape and furnished with three keys, the depression of which puts extra lengths of tubing in connection with the er One key lowers the fundamental note of the horn half a tone; the second, a full tone; the third, a tone and a half If the first and third are pressed down together, the note sinks two tones; if the second and third, two and a half tones; and siives a drop of three tones The performer thus has seven possible fundamental notes, and several harmonics of each of these at his command; so that by a proper manipulation of the keys he can run up the chromatic scale