Perc. instr. similar to marimba. Tuned metal bars, laid out like pf. kbd., are struck by the player holding small padded hammer in each hand. Beneath bars are resonators fitted with lids which constantly open and close electrically, giving pulsating sound to any of the metal bars when struck by the player. Compass f–f′′′. Used first in jazz (Lionel Hampton a celebrated player), then frequently in symphonic and operatic works, e.g. by Berg in Lulu, Vaughan Williams, McCabe, Britten, Milhaud, Henze, Messiaen, Tippett, and Boulez.