(German: “set of bells”), percussion instrument, originally a set of graduated bells, later a set of tuned steel bars (i.e., a metallophone) struck with wood, ebonite, or, sometimes, metal hammers. The bars are arranged in two rows, the second corresponding to the black keys of the piano. The range is 2¹/₂ or, occasionally, 3 octaves, the highest note normally the fourth C above middle C (written two octaves lower). Military bands use a portable form with a lyre-shaped frame, called a bell lyre. A glockenspiel may be fitted with a keyboard mechanism so that chords can be played. The glockenspiel became part of the orchestra in the 18th century.