The monochord, a primitive, single-stringed scientific instrument, attributed to Pythagoras, used as a way of teaching harmonics, measuring musical intervals, tuning scales and encouraging experimentation. It is thought that Pythagoras used the monochord to delineate the three Western Scales (diatonic, chromatic, and enharmonic), illustrating how numerical ratios could be visualized with sound. The single string was typically plucked, though later developments would offer other variations, including the use of a bow. The introduction of a sound box to enhance the lower-frequency response of the single string led to the invention of the soundboard.