In the 1930s, Cowell's student Lou Harrison utilized keyboard clusters in several works such as his Prelude for Grandpiano (1937). At least as far back as 1942, John Cage, who also studied under Cowell, began writing piano pieces with cluster chords; "In the Name of the Holocaust", from December of that year, includes chromatic, diatonic, and pentatonic clusters. Olivier Messiaen's "Vingt regards sur l'enfant Jésus" (1944), often described as the most important solo piano piece of the first half of the twentieth century, employs clusters throughout. They would feature in numerous subsequent piano works, by a range of composers. Karlheinz Stockhausen's "Klavierstück X" (1961) makes bold, rhetorical use of chromatic clusters, scaled in seven degrees of width, from three to thirty-six semitones, as well as ascending and descending cluster arpeggios and cluster glissandi. Written two decades later, his "Klavierstück XIII" employs many of the same techniques, along with clusters that call for the pianist to sit down on the keyboard. George Crumb's "Apparitions, Elegiac Songs, and Vocalises for Soprano and Amplified Piano" (1979), a setting of verse by Walt Whitman, is filled with clusters, including an enormous one that introduces three of its sections. The piano part of the second movement of Joseph Schwantner's song cycle "Magabunda" (1983) has perhaps the single largest chord ever written for an individual instrument: all 88 notes on the keyboard.