noun
set piece; compulsory piece
A musical piece assigned as a task, especially in competitions, auditions, or exams.
今年のコンクールの課題曲はショパンのエチュードです。
This year's competition set piece is a Chopin étude.
ピアノの発表会で課題曲を弾く。
I will play the assigned piece at the piano recital.