a musical instrument with only one string, used to try the variety and proportion of sounds. It is formed of a rule, divided and subdivided into several parts, on which there is a moveable string stretched upon two bridges at each extreme. In the middle between these is a moveable bridge, by means of which, in applying to it 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. There are also monochords with 48 fixed bridges. This instrument is also called the harmonical canon, or the canonical rule, because it serves to measure the degrees of gravity or acuteness.—Monochord is also used for any musical instrument that consists of only one string or chord; in this sense the trumpet marine may properly be called a monochord.