The monochord consists of a metal string stretched over a hollow resonating body. Using a movable bridge the string can be divided into two portions whose lengths may be set at any ratio to give various pitches G and musical intervals when plucked. According to tradition, the ancient Greek philosopher Pythagoras (fl. 4th century BC) discovered the correspondence between simple ratios of string length and consonant G musical intervals. Dividing the string into sections in the ratios 2:1 or 3:2, for example, yields the intervals of a perfect octave andperfect fifth G respectively.