カバー曲[kabaakyoku] remake of another artist's song (a "cover")
サイン曲線[sainkyokusen] sinusoid
愛唱曲[aishoukyoku] favourite song
委曲[ikyoku] details
一曲[ikkyoku] tune (melody, piece of music)

迂曲[ukyoku] meander
円曲[enkyoku] roundabout way (of speaking or working)
円錐曲線[ensuikyokusen] conic curve
円舞曲[enbukyoku] waltz (composition)
演曲[enkyoku] musical program

箏柱[kotoji] bridge of a koto
箏曲[soukyoku] koto music
古箏[kosou] Guzheng (type of ancient Chinese zither)

俗箏[zokusou] modern koto (in contrast to the gagaku koto or gakuso)
楽箏[gakusou] ancient type of koto with 13 strings used in Gagaku music
箏曲家[soukyokusha] koto player