It seems like an intimidating requirement: "Must be able to play George Hamilton Green exercises five and ten without stopping in all major and natural minor keys." This is what would be expected of a music student in "Applied Percussion 119" class, for example, and it is just one reflection of the over-size image Green has in percussion music, specifically the history of the xylophone and vibraphone. The former instrument was one of a group of varied percussion that was added to the classical orchestra in the 19th century, also including tuned bells and glockenspiel. It would not be until Green's recordings in the 1920s that the full potential of these instruments would be realized. Keyboard percussionists ever since have been building on the Green groundwork which includes vintage recordings, a large repertoire of compositions, and several instructional texts that have remained essential. Some vibraphonists taught themselves to play simply by using Green's recordings, among them the great jazzman Red Norvo, after pilfering Green sides from his parents' record collection.