George Crumb (b. 1929) is an American composer of avant-garde music. He is noted as an explorer of unusual timbres, alternative forms of notation, and extended instrumental and vocal techniques. Examples include a seagull effect for the cello (e.g. Vox Balaenae), metallic vibrato for the piano (e.g. Five Pieces for Piano), and using a mallet to play the strings of a contrabass (e.g. Madrigals, Book I), among numerous others.
After initially being influenced by Anton Webern, Crumb became interested in exploring unusual timbres. He often asks for instruments to be played in unusual ways and several of his pieces, although written for standard chamber music ensembles, such as Black Angels (string quartet) or Ancient Voices of Children (mixed ensemble), call for electronic amplification. Crumb defines music as "a system of proportions in the service of spiritual impulse."