Question: Symphony No. 3 was written by a musician who was proficient on what instrument?

Context articles: Carl Nielsen
Elliott Smith
Lead instrument
Symphony No. 3 (Nielsen)
Symphony
Feró Nagy
Tenor violin
Hugo Walter Voigtlander
Steven Mead
Georges Mager

Carl August Nielsen (] ; 9 June 18653 October 1931) was a Danish musician, conductor and violinist, widely recognized as his country's most prominent composer.
Steven Paul "Elliott" Smith (August 6, 1969 – October 21, 2003) was an American singer, songwriter, and musician.
 Smith was born in Omaha, Nebraska, raised primarily in Texas, and lived for much of his life in Portland, Oregon, where he first gained popularity.
 Smith's primary instrument was the guitar, though he was also proficient with piano, clarinet, bass guitar, drums, and harmonica.
 Smith had a distinctive vocal style, characterized by his "whispery, spiderweb-thin delivery", and used multi-tracking to create vocal layers, textures, and harmonies.
The term lead instrument carries a variety of connotations.
 A lead instrument could be a reference to an instrument that plays the melody of a piece, an instrument that has been designed for this purpose, such as clarinet or violin, or a specific member of an orchestra that is featured as the most proficient musician of the group.
 In digital music composition, lead may refer to the tone quality that is applied to a signal.
The Danish composer Carl Nielsen wrote his Symphony No. 3 "Sinfonia Espansiva", Op.
 27, FS 60, between 1910 and 1911.
 Around 33 minutes in length, it is unique in his symphonic output for having vocal parts, specifically wordless solos for soprano and baritone in the second movement.
A symphony is an extended musical composition in Western classical music, most often written by composers for orchestra.
 Although the term has had many meanings from its origins in the ancient Greek era, by the late 18th century the word had taken on the meaning common today: a work usually consisting of multiple distinct sections or movements, often four, with the first movement in sonata form.
 Symphonies are scored for string (violin, viola, cello and double bass), brass, woodwind, and percussion instruments which altogether number about 30–100 musicians.
 Symphonies are notated in a musical score, which contains all the instrument parts.
 Orchestral musicians play from parts which contain just the notated music for their instrument.
 A small number of symphonies also contain vocal parts (e.g., Beethoven's Ninth Symphony).
Ferenc "Feró" Nagy (born January 14, 1946 in Letenye, Hungary) is a Hungarian rock singer and musician.
 Although not proficient on any instrument, he can play the guitar, the harmonica, the saxophone and the piano.
A tenor violin (or tenor viola) is an instrument with a range between those of the cello and the viola.
 An earlier development of the evolution of the violin family of instruments, the instrument is not standard in the modern symphony orchestra.
 Its tuning, typically G–D–A–E – an octave below the traditional violin, places the range between the cello and viola and thus is sometimes confused with the modern baritone violin which has the same tuning on the standard violin body.
 As a formal development, the 17th-century tenor violin existed as an instrument with a body larger than a viola but with a short neck.
 In earlier designs, the tenor was played upright in the musician's lap.
 Tenor violin parts were written in tenor clef (4th line C-clef).
Hugo Walter Voigtlander (November 8, 1859 – January 7, 1933) was a German-American musician who played violin, viola, and viola d'amore.
 He was also an instrument maker, and a collector and arranger of viola d'amore music.
 As a youth he studied at the Royal Conservatory of Music in Leipzig and played violin and viola in several professional orchestras in Germany.
 He emigrated to the United States in 1885 where he spent ten years playing viola and viola d'amore with various professional chamber groups in and around Detroit, Michigan.
 He then spent two years in Pittsburgh, Pennsylvania playing in the Pittsburgh Symphony Orchestra, and in 1897 moved to New York City, where he played in a number of professional orchestras.
 In addition to playing viola d'amore, Walter Voigtlander taught viola d'amore, and made and collected numerous arrangements for the instrument.
Steven Mead (born 1962 in Bournemouth, England) is an English virtuoso euphonium soloist and teacher who has played an important role in achieving worldwide recognition of the instrument.
 He has played solo concerti with symphony orchestras, including: the Stuttgart Philharmonic Orchestra, the Trondheim Symphony Orchestra, Lahti Symphony Orchestra and Helsinki Philharmonic, Capella Cracoviensis, the Minneapolis Pops Orchestra and the Japan Chamber Orchestra.
 He has premiered works by Martin Ellerby, Torstein Aagaard-Nilsen, Vladimir Cosma, Goff Richards, John Reeman, Rolf Rudin and Philip Sparke, amongst others.
 Goff Richards' "Pilatus", Aagaard-Nilsen's "Concerto for Euphonium and Orchestra", Reeman's "Sonata for Euphonium" and Ellerby's "Euphonium Concerto" were all written expressly for Mead.
Georges C. Mager (1885–1950) was a French musician, and principal trumpet with the Boston Symphony Orchestra from 1919 until his death in 1950.
 He was a renowned trumpeter in Paris before the First World War, playing at the Paris Opera, Concerts Lamoureux, and the Concerts of the Society of the Conservatory.
 He also had an alternate career as a singer in the duo with his wife Claire, a well-known soprano, and had hoped for an operatic career.
 After serving in the French army during the war he came to America as flugelhorn soloist with the Garde Republicaine Band and was engaged to play in the Boston Symphony, first as a violist, since there was no vacancy for trumpet, sharing a stand with Arthur Fiedler.
 He assumed the first trumpet position in 1920.
 Trained in France, he was a student of J. Mellet (a student of Jean-Baptiste Arban) at the Paris Conservatory.
 He was an advocate of use of the C trumpet as an orchestral instrument and had great influence on its development and acceptance in America, working most notably with Vincent Bach.
 He also was the first trumpeter in America to play Bach's Brandenburg Concerto in the original high tessitura.
 Mager was on the faculty of the New England Conservatory, and was a teacher to some of the most influential trumpeters of the mid-twentieth century, including Adolph Herseth (who became principal trumpet of the Chicago Symphony Orchestra), Roger Voisin (who replaced Mager as principal trumpet of the Boston Symphony Orchestra in 1950, Bernard Adelstein (who became principal trumpet of the Cleveland Orchestra), Irving Sarin (who became principal trumpet of the Pittsburgh Symphony Orchestra and respected teacher in his own right), and Renold Schilke (who joined the trumpet section of the Chicago Symphony Orchestra and later became an important trumpet maker).
 He was also teacher to jazz trumpeter Leon Merian.