Question: Which influential composer of piano music was active later in the 20th century: Dmitri Shostakovich or Philip Glass?
Context: Sally Whitwell (born 1974) is an Australian classical music pianist, composer, arranger, conductor and teacher.  She has released four solo albums, "Mad Rush: Piano Music of Philip Glass" (3 June 2011), "The Good, the Bad and the Awkward" (18 May 2012), "All Imperfect Things: The Piano Music of Michael Nyman" (6 September 2013) and ""I Was Flying"" (5 June 2015) all on the ABC Classics record label.  All three albums have peaked in the top 5 on the ARIA Charts' Classical Albums. The Symphony No. 13 in B-flat minor (Op. 113, subtitled "Babi Yar") by Dmitri Shostakovich was completed on July 20, 1962 and first performed in Moscow on 18 December 1962 by the Moscow Philharmonic Orchestra and the basses of the Republican State and Gnessin Institute Choirs, under Kirill Kondrashin (after Yevgeny Mravinsky refused to conduct the work).  The soloist was Vitali Gromadsky.  This work has been variously called a song cycle and a choral symphony since the composer included settings of poems by Yevgeny Yevtushenko that concerned the World War II Babi Yar massacre and other topics.  The five poems Shostakovich set to music (one poem per movement) are earthily vernacular and cover every aspect of Soviet life. Sofia Moshevich (Hebrew: סופיה מושביץ'‎ ‎ ; born 1949) is a Ukrainian-born pianist, teacher and researcher who lived in Moscow, Jerusalem and Johannesburg before emigrating to Canada where she now lives in Toronto.  Since the early 1970s, she has taken a special interest in the Russian composer Dmitri Shostakovich, making a careful analysis of his recorded performances as a pianist.  Two books document the results of her work: "Dmitri Shostakovich, Pianist" and "Shostakovich's Music for Piano Solo, Interpretation and Performance".  She also contributed a chapter on piano music to "A Shostakovich Companion", edited by Michael Mishra. Mstislav Leopoldovich "Slava" Rostropovich (Russian: Мстисла́в Леопо́льдович Ростропо́вич , "Mstislav Leopol'dovič Rostropovič", ] ; 27 March 192727 April 2007) was a Soviet and Russian cellist and conductor.  He is considered to be one of the greatest cellists of the 20th century.  In addition to his interpretations and technique, he was well known for both inspiring and commissioning new works, which enlarged the cello repertoire more than any cellist before or since.  He inspired and premiered over 100 pieces, forming long-standing friendships and artistic partnerships with composers including Dmitri Shostakovich, Sergei Prokofiev, Henri Dutilleux, Witold Lutosławski, Olivier Messiaen, Luciano Berio, Krzysztof Penderecki, Alfred Schnittke, Norbert Moret, Andreas Makris and Benjamin Britten. Solo Piano (1989) is an album of piano music composed and performed by Philip Glass.  It was produced by Kurt Munkacsi. Ian MacCormick (known by the pseudonym Ian MacDonald; 3 October 1948 – 20 August 2003) was a British music critic and author, best known for both "", his critical history of the Beatles which borrowed techniques from art historians, and "The New Shostakovich", a study of Russian composer Dmitri Shostakovich.  MacDonald was instrumental in popularising Nick Drake during the late 1970s and early 1980s. Philip Morris Glass (born January 31, 1937) is an American composer.  He is widely regarded as one of the most influential musicians of the late 20th century. Dmitri Dmitriyevich Shostakovich (Russian: Dmitriy Dmitrievich Shostakovich , ] ; 25 September [O.S. 12 September] 1906 9 August 1975) was a Russian composer and pianist.  He is regarded as one of the major composers of the 20th century. A fortepiano ] is an early piano.  In principle, the word "fortepiano" can designate any piano dating from the invention of the instrument by Bartolomeo Cristofori around 1700 up to the early 19th century.  Most typically, however, it is used to refer to the late-18th to early-19th century instruments for which Haydn, Mozart, and the younger Beethoven wrote their piano music.  Starting in Beethoven's time, the fortepiano began a period of steady evolution, culminating in the late 19th century with the modern grand.  The earlier fortepiano became obsolete and was absent from the musical scene for many decades.  In the 20th century the fortepiano was revived, following the rise of interest in historically informed performance.  Fortepianos are built for this purpose today in specialist workshops. Bruno Bjelinski (born Bruno Weiss; 1 November 1909 – 3 September 1992) was one of a most influential Croatian composers in the 20th century.  He was extremely prolific as a composer.  His unique musical style was built upon the music of Poulenc, Hindemith, Ravel and Milhaud.  He developed his own and recognizable musical language with the elements of neoclassicism.  Bjelinski composed six operas, three ballets, 15 symphonies, 2 cello concertos, a cantata, piano music, songs, chamber music, and concertos for piano, violin, viola, bassoon, flute, and piano duo.  He also composed music for the Croatian football movie "Plavi 9".
Answer: Philip Morris Glass