4. The essential characteristic of the pipe-organ is a number of sets or registers of pipes called stops, each set being capable (usually) of sounding the entire chromatic scale through a range of five or six octaves. Thus for example when the stop melodia is drawn (by pulling out a stop-knob or tilting a tablet), one set of pipes only, sounds when the keyboard is played on: but if the stop flute is drawn with melodia, two pipes speak every time a key is depressed. Thus if an organ has forty speaking stops, all running through the entire keyboard, then each time one key is depressed forty pipes will speak, and if a chord of five tones is played, two hundred pipes will speak. The object of having so many pipes is not merely to make possible a very powerful tone, but, rather, to give greater variety of tone-color.
The pipe-organ usually has a pedal keyboard on which the feet of the performer play a bass part, this part often sounding an octave (or more) lower than the notes indicate.
An eight-foot stop on the organ produces tones of the same pitches as the piano when corresponding keys are struck: A four-foot stop sounds tones an octave higher and a two-foot stop tones two octaves higher. A sixteen-foot stop sounds tones an octave lower than the piano, and a thirty-two foot stop, tones two octaves lower, while some organs have also a sixty-four foot stop which sounds three octaves lower. This gives the organ an exceedingly wide range, its compass being greater than that of any other single instrument, and comparable in both range of pitches and variety of color only with the modern orchestra.
Modern pipe-organs always have a number of combination pedals or pistons (usually both), by means of which the organist is enabled to throw on a number of stops with one movement. The selection and use of suitable stops, couplers, combinations, etc., is called registration.
5. The instruments mentioned at the beginning of this appendix as belonging to the second class are more familiar in connection with ensemble playing, being commonly associated with either band or orchestra.
6. A band is a company of musicians all of whom play upon either wind or percussion instruments, the main body of tone being produced by the brass and wood-wind divisions.
Sousa's band is usually made up in somewhat the following manner: 4 flutes and piccolos, 12 B♭ clarinets, 1 E♭ clarinet, 1 alto clarinet, 1 bass clarinet, 2 oboes, 2 bassoons, 2 sarrusophones, 4 saxophones, 4 cornets, 2 trumpets, 1 soprano saxhorn (fluegelhorn), 4 French horns, 4 trombones, 2 contra-bass tubas, 4 tubas, 1 snare drum, 1 bass drum, 2 kettle drums, cymbals, triangle, bells, castanets, xylophone, etc.
7. An orchestra is a company of musicians performing upon stringed instruments as well as upon wind and percussion. It is differentiated from the band by the fact that the main body of tone is produced by the strings.
There are four classes of instruments in the orchestra, viz., strings, wood-wind, brass (wind) and percussion. In addition to these four classes, there is the harp, which although a stringed instrument, does not belong in the same group as the other strings because the manner of producing the tone is altogether different.
8. In the first group (the strings) are found the first and second violins, viola, violoncello (usually spelled cello), and double-bass. The first and second violins are identical in every way (but play different parts), while the other members of the family merely represent larger examples of the same type of instrument.