Question: What did the Russian composer who composed Pictures at an Exhibition invest 

Context paragraphs:
Night on Bald Mountain: Night on Bald Mountain (Russian: Ночь на лысой горе, "Noch′ na lysoy gore" ), also known as Night on the Bare Mountain, is a series of compositions by Modest Mussorgsky (1839–1881).  Inspired by Russian literary works and legend, Mussorgsky composed a "musical picture", "St. John's Eve on Bald Mountain" (Russian: Иванова ночь на лысой горе, "Ivanova noch′ na lysoy gore" ) on the theme of a witches' sabbath occurring on St. John's Eve, which he completed on that very night, 23 June 1867.  Together with Nikolay Rimsky-Korsakov's "Sadko" (1867), it is one of the first tone poems by a Russian composer.

Alexander Radvilovich: Alexander Yuryevich Radvilovich (Russian: Александр Юрьевич Радвилович ; born 1955) is a Russian composer, pianist and teacher from Leningrad (now Saint Petersburg) from which Conservatory he also graduated at which he was under guidance from Sergei Slonimsky.  In 1992 and 1994 respectively he was the first ever composer of Russian origin to get education at the International New Music in Darmstadt.  He is known for his symphonies of two of his own poems called "Legend About Violinist" and "Pushkin".  At one time, after reading Fyodor Dostoyevsky he composed a string quartet called "The Boy at Christ’s New Year Celebration" and also designed a mini opera called "Let’s Write Fairy-tale".  He also composed an opera called "Hindrance" which was based on Danii Kharms' poem "Ruin of the Gods".  Currently he is a member of both Russian Composer’s and Saint Petersburg Composer's Unions and works as music pedagogue at the Humanitarian University of the Petersburg Conservatory.  On occasion, he tours the world as composer, pianist and leader of the Sound Ways which he also founded back in 1989.  His music is published by various labels in countries such as Russia, the Netherlands and the United States.

Modest Mussorgsky: Modest Petrovich Mussorgsky (Russian: Моде́ст Петро́вич Му́соргский ; ] ; 21 March [O.S. 9 March] 1839 – 28 March [O.S. 16 March] 1881 ) was a Russian composer, one of the group known as "The Five".  He was an innovator of Russian music in the romantic period.  He strove to achieve a uniquely Russian musical identity, often in deliberate defiance of the established conventions of Western music.

Alexander Scriabin: Alexander Nikolayevich Scriabin ( ; Russian: Алекса́ндр Никола́евич Скря́бин , ] ; 6 January 1872 [O.S. 25 December 1871] – 27 April [O.S. 14 April] 1915 ) was a Russian composer and pianist.  Scriabin, who was influenced early in his life by the works of Frédéric Chopin, composed works that are characterised by a highly tonal idiom (these works are associated with his "first stage" of compositional output).  Later in his career, independently of Arnold Schoenberg, Scriabin developed a substantially atonal and much more dissonant musical system, which accorded with his personal brand of mysticism.  Scriabin was influenced by synesthesia, and associated colours with the various harmonic tones of his atonal scale, while his colour-coded circle of fifths was also influenced by theosophy.  He is considered by some to be the main Russian Symbolist composer.

Symphony No. 2 (Rachmaninoff): Symphony No. 2 in E minor, Op. 27 is a symphony by the Russian composer Sergei Rachmaninoff, written in 1906–07.  The premiere was conducted by the composer himself in Saint Petersburg on 8 February 1908.  Its duration is approximately 60 minutes when performed uncut; cut performances can be as short as 35 minutes.  The score is dedicated to Sergei Taneyev, a Russian composer, teacher, theorist, author, and pupil of Pyotr Ilyich Tchaikovsky.  Alongside his Piano Concerto No. 2 and Piano Concerto No. 3, this symphony remains one of the composer's best known compositions.

Kamarinskaya: Kamarinskaya (Russian: камаринская ) is a Russian traditional folk dance, which is mostly known today as the Russian composer Mikhail Glinka's composition of the same name.  Glinka's "Kamarinskaya", written in 1848, was the first orchestral work based entirely on Russian folk song and to use the compositional principles of that genre to dictate the form of the music.  It became a touchstone for the following generation of Russian composers ranging from the Western-oriented Pyotr Ilyich Tchaikovsky to the group of nationalists known collectively as The Five and was also lauded abroad, most notably by French composer Hector Berlioz.

Pictures at an Exhibition: Pictures at an Exhibition (Russian: Картинки с выставки – Воспоминание о Викторе Гартмане , "Kartínki s výstavki – Vospominániye o Víktore Gártmane" , "Pictures from an Exhibition – A Remembrance of Viktor Hartmann"; French: "Tableaux d'une exposition" ) is a suite of ten pieces (plus a recurring, varied Promenade) composed for the piano by Russian composer Modest Mussorgsky in 1874.

Pyotr Ilyich Tchaikovsky: Pyotr Ilyich Tchaikovsky ( ; Russian: Пётр Ильи́ч Чайко́вский ; 25 April/7 May 1840 – 25 October/6 November 1893), often anglicized as Peter Ilich Tchaikovsky, was a Russian composer of the romantic period, some of whose works are among the most popular music in the classical repertoire.  He was the first Russian composer whose music made a lasting impression internationally, bolstered by his appearances as a guest conductor in Europe and the United States.  Tchaikovsky was honored in 1884, by Emperor Alexander III, and awarded a lifetime pension.

Pictures at an Exhibition (disambiguation): Pictures at an Exhibition is a suite of ten piano pieces composed by Modest Mussorgsky.

Alexander Serov: Alexander Nikolayevich Serov (Russian: Алекса́ндр Никола́евич Серо́в , Saint Petersburg, 23 January [O.S. 11 January] 1820 – Saint Petersburg, 1 February [O.S. 20 January] 1871 ) was a Russian composer and music critic.  He is notable as one of the most important music critics in Russia during the 1850s and 1860s and as the most significant Russian composer in the period between Dargomyzhsky's "Rusalka" and the works of Rimsky-Korsakov, Mussorgsky, and Tchaikovsky.

Supporting paragraphs: Pictures at an Exhibition (disambiguation) Modest Mussorgsky
Answer: Russian music