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

哀歌[aika] lament (song)
愛唱歌[aishouka] (one's) favourite song
詠歌[eika] poem (esp. tanka)
艶歌[enka] enka
応援歌[ouenka] rooters' song

歌い合う[utaiau] to sing responsively
歌い上げる[utaiageru] to sing at the top of one's voice
歌詠み[utayomi] tanka composer
歌会[utakai] poetry party or competition