MONOCHORD

, a musical instrument with only one string, used by the Ancients to try the variety and proportion of sounds. It was formed of a rule, divided and subdivided into several parts, on which there is a moveable string stretched over two bridges at the extremes of it. In the interval between these is a sliding or moveable bridge, by means of which, in applying it to the different divisions of the line, the sounds are found to bear the same proportion to each other, as the division of the line cut by the bridge. This instrument is also called the harmonical canon, or the canouical rule, because it serves to measure the degrees of gravity or acuteness. Ptolomy examines his harmonical intervals by the Monochord. When the chord was divided into two equal parts, so that the parts were as 1 to 1, they called them unisons; but if they were as 2 to 1, they called them octaves or diapasons; when they were as 3 to 2, they called them diapentes, or fifths; if they were as 4 to 3, they called them diatessarons, or fourths; if the parts were as 5 to 4, they called them diton, or majorthird; but if they were as 6 to 5, they were called a dcmi-diton, or minor-third; and lastly, if the parts were as 24 to 25, a demitone, or dicze.

The Monochord, being thus divided, was properly what they called a system, of which there were many kinds, according to the different divisions of the Monochord.

Monochord is also used for any musical instrument consisting of only one chord or string. Such is the Trump-marine.