CHAPTER VIII.
The construction of the organistrum requires but little explanation. A glance at the finger-board reveals at once that the different tones were obtained by raising the keys placed on the neck under the strings, and that the keys were raised by means of the handles at the side of the neck. Of the two bridges shown on the body, the one situated nearest the middle was formed by a wheel in the inside, which projected through the sound-board. The wheel which slightly touched the strings vibrated them by friction when turned by the handle at the end. The order of intervals was c, d, e, f, g, a, b-flat, b-natural, c, and were obtainable on the highest string. There is reason to suppose that the other two strings were generally tuned a fifth and an octave below the highest. The organistrum may be regarded as the predecessor of the hurdy-gurdy, and was a rather cumbrous contrivance. Two persons seem to have been required to sound it, one to turn the handle and the other to manage the keys. Thus it is generally represented in mediæval concerts.
The monochord (p. 100) was mounted with a single string stretched over two bridges which were fixed on an oblong box. The string could be tightened or slackened by means of a turning screw inserted into one end of the box. The intervals of the scale were marked on the side, and were regulated by a sort of movable bridge placed beneath the string when required. As might be expected, the monochord was chiefly used by theorists; for any musical performance it was but little suitable. About a thousand years ago when this monochord was in use the musical scale was diatonic, with the exception of the interval of the seventh, which was chromatic inasmuch as both b-flat and b-natural formed part of the scale. The notation on the preceding page exhibits the compass as well as the order of intervals adhered to about the tenth century.
This ought to be borne in mind in examining the representations of musical instruments transmitted to us from that period.
As regards the wind instruments popular during the middle ages, some were of quaint form as well as of rude construction.
The chorus, or choron, had either one or two tubes, as in the woodcut page 101. There were several varieties of this instrument; sometimes it was constructed with a bladder into which the tube is inserted; this kind of chorus resembled the bagpipe; another kind resembled the poongi of the Hindus, mentioned page 51. The name chorus was also applied to certain stringed instruments. One of these had much the form of the cithara, page 86. It appears however, probable that chorus or choron originally designated a horn (Hebrew, Keren; Greek, Keras; Latin, cornu).
The flutes of the middle ages were blown at the end, like the flageolet. Of the syrinx there are extant some illustrations of the ninth and tenth centuries, which exhibit the instrument with a number of tubes tied together, just like the Pandean pipe still in use. In one specimen engraved (page 102) from a manuscript of the eleventh century the tubes were inserted into a bowl-shaped box. This is probably the frestele, fretel, or fretiau, which in the twelfth and thirteenth centuries was in favour with the French ménétriers.