The term 'Liszt Opus' refers to the works of the Hungarian composer Franz Liszt. One of his most famous works is the Etude, which is a short musical composition that focuses on a particular technique or skill. The Etude is often used as an exercise for students of music, and it is usually composed in a single movement. Liszt's Etudes are considered to be some of the most difficult pieces of music ever written, and they are highly regarded by musicians and music lovers alike.