Saxophones appear in some scores from the late 19th century onwards. While appearing only as featured solo instruments in some works, for example Maurice Ravel's orchestration of Modest Mussorgsky's Pictures at an Exhibition and Sergei Rachmaninoff's Symphonic Dances, the saxophone is included in other works, such as Ravel's Boléro, Sergei Prokofiev's Romeo and Juliet Suites 1 and 2 and many other works as a member of the orchestral ensemble. The euphonium is featured in a few late Romantic and 20th-century works, usually playing parts marked "tenor tuba", including Gustav Holst's The Planets, and Richard Strauss's Ein Heldenleben.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): Who wrote The Planets?
Gustav Holst