Pluto
http://en.wikipedia.org/wiki/The_Planets
"Although discovered Pluto WAS DURING Holst's lifetime, in 1930, Holst Expressed Interested in writing not to Movement for it. In 2000, the Hall Orchestra commissioned composer Colin Matthews, a Holst specialist, to write a new eighth movement, which Matthews entitled Pluto, the Renewer. Dedicated to Imogen Holst, Gustav Holst's daughter, it was first performed in Manchester on May 11, 2000, with Kent Nagano conducting the Hallé Orchestra. Matthews changed the ending of Neptune into a transition to Pluto. In August 2006 Pluto's status was changed from a planet to a dwarf planet by the International Astronomical Union (IAU), so Holst's original work is once again a complete representation of all the known planets in the solar system (save Earth). After the reclassification Matthews said that he might ban future performances of his movement, although he later made it clear that he was joking. However, since Pluto is no longer classified as a planet, Holst's original work may be considered complete as he created it.»
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http://www.peabody.jhu.edu/743
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At around this time (1913), Stravinsky premiered the Rite of Spring, sparking riots in Paris and caustic criticism in London. A year later, Holst first heard Schoenberg’s Five Pieces for Orchestra, an ‘ultra-modern’ set of five movements employing ‘extreme chromaticism’ (the consistent use of all 12 musical notes).
