Question: Who was the original composer of "Pictures at an Exhibition"?

Context articles: Nightmare Revisited
Giovanni Girolamo Kapsperger
Monster Surf
Uns ist ein Kind geboren, BWV 142
Cao Văn Lầu
Haste to the Wedding (jig)
Mihály Erdélyi
Storm Over the Nile
Leo Funtek
Modest Mussorgsky

Nightmare Revisited is a cover album of songs and score from the 1993 Disney animated film "The Nightmare Before Christmas".
 It was released on September 30, 2008 by Walt Disney Records to commemorate the film's 15th anniversary of its theatrical release.
 In addition to the album's eighteen covers are two re-recordings by original composer Danny Elfman, of the "Opening" and "Closing" tracks.
 One song featured on the album, Marilyn Manson's "This Is Halloween", was previously released nearly two years earlier, on the 2006 reissue of the film's original soundtrack which, featuring five covers of songs from the film, acted as a precursor to "Nightmare Revisited".
 The album also features Korn — in their last collaboration before their hiatus — covering "Kidnap the Sandy Claws" which is also their first recording to feature Ray Luzier on drums.
 Enhanced content on the disc features the trailer of "The Nightmare Before Christmas", as well.
Giovanni Girolamo Kapsperger (also: "Johann(es) Hieronymus Kapsberger" or "Giovanni Geronimo Kapsperger"; c. 1580 – 17 January 1651) was a German-Italian virtuoso performer and composer of the early Baroque period.
 A prolific and highly original composer, Kapsberger is chiefly remembered today for his lute and theorbo ("chitarrone") music, which was seminal in the development of these as solo instruments.
Monster Surf is a Gary Hoey album released in 2005.
 It consists of 14 instrumental tracks, 11 of which are cover versions of surf music hits.
 Dick Dale, the track's original composer, makes a guest appearance on "Misirlou".
Uns ist ein Kind geboren (Unto us a child is born), BWV 142, is a Christmas cantata formerly attributed to Johann Sebastian Bach.
 The text is based on a libretto by Erdmann Neumeister first published in 1711.
 Since the cantata was first published by the Bach-Gesellschaft in the nineteenth century, Bach scholars, including Johannes Schreyer, Arnold Schering and Alfred Dürr, have not accepted this attribution, although the identity of the original composer has not been established.
 In the late twentieth century it was withdrawn from the Neue Bach Ausgabe, replaced by a detailed historical commentary on authenticity and attribution by Andreas Glöckner.
 Because of uncertainty of attribution, it remains in Anhang II of the BWV.
 It is now considered plausible that Johann Kuhnau, Bach's predecessor as Thomaskantor in Leipzig, may have composed the cantata, as originally suggested by .
Cao Văn Lầu (1892–1976), also known as Sáu Lầu ("Lầu the Sixth" in Vietnamese), was a Vietnamese musician.
 He was the original composer of the song vong co which started a new genre of cai luong music in the 1920s.
"Haste to the Wedding" is a jig tune in the Scottish and Irish musical traditions.
 The tune originated during the 18th century, although its original composer is not certain.
 Written in the standard 8-bar AABB format of Gaelic music, it is traditionally performed on the fiddle, but is a simple tune which can be performed on a variety of instruments, and is frequently adapted for session music.
 The tune has also been used as the basis for songs, and as musical accompaniment for ceili dances of the same name.
Mihály Erdélyi (May 28, 1895 - January 27, 1979) was a Hungarian composer, lyricist, actor, and producer, particularly prolific in the interwar period.
 Erdélyi was born in Szeged in 1895 and began a career as an actor then a stage producer, but became most famous for his operettas, including "Csókos regiment" (1932), "Fehérvári huszárok" (1933), "A csavargólány" (1936), "Sárgapitykés közlegény" (1937), "A zimberi-zombori szépasszony" (1939), "Sárgarigófészek" (1940), "Vedd le a kalapod a honvéd előtt" (1942), and "A két kapitány" (1943).
 Many of his songs have entered the Hungarian musical canon as folk music, often without an awareness of the original composer.
Storm Over the Nile is a 1955 film adaptation of the novel "The Four Feathers", directed by Terence Young and Zoltan Korda.
 The film not only extensively used footage of the action scenes from the 1939 film version stretched into CinemaScope, but is a shot-for-shot, almost line-for-line remake of the earlier film, which was also directed by Korda.
 Several pieces of music by the original composer Miklos Rozsa were also utilised.
 It featured Anthony Steel, Laurence Harvey, James Robertson Justice, Mary Ure, Ian Carmichael, Michael Hordern and Christopher Lee.
 The film was shot on location in the Sudan.
Leo Funtek (August 21, 1885 — January 13, 1965) was a Slovenian violinist, conductor and arranger.
 He is best known for work as a music professor and for his 1922 arrangement of Modest Mussorgsky's piano suite "Pictures at an Exhibition".
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.