noun
joint composition; co-written piece
Refers to a musical or artistic work created by two or more people together. Often used in contexts like songwriting credits or collaborative projects.
この曲は二人の共作曲です。
This song is a joint composition by the two of them.
彼女は有名な作曲家との共作曲を発表した。
She released a co-written piece with a famous composer.
共作 is a general term for co-creation or collaboration, not limited to music. 共作曲 narrows the focus to a composed musical work.
Compound of 共 (きょう, 'together') + 作曲 (さっきょく, 'composition'). The reading きょうさくきょく reflects the standard on'yomi of the kanji.