noun
A musical composition for the dead, often used in classical music contexts. The term is straightforward and not particularly rare.
モーツァルトの鎮魂曲はとても有名です。
Mozart's Requiem is very famous.
Katakana loanword for 'requiem', often used in modern or pop culture contexts, while 鎮魂曲 is the native kanji term more common in classical music.
Compound of 鎮魂 (ちんこん, 'repose of souls') and 曲 (きょく, 'musical piece'). The word is a direct translation of the Western concept of a requiem mass set to music.