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

し難い[shinikui] hard to do
一難[ichinan] one difficulty
火難[kanan] fire calamity
海難[kainan] shipwreck
患難[kannan] affliction

危難[kinan] peril
及び難い[oyobigatai] hard to attain to
救難[kyuunan] rescue
救難ヘリコプター[kyuunanherikoputaa] rescue helicopter
苦難[kunan] suffering