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

 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. The Danish composer Carl Nielsen wrote his Symphony No. 3 "Sinfonia Espansiva", Op. <SEP> Carl August Nielsen (] ; 9 June 18653 October 1931) was a Danish musician, conductor and violinist, widely recognized as his country's most prominent composer. <SEP> 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. <SEP> 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).