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

直向[hitamuki] earnest
安直[anchoku] inexpensive
一直[icchoku] lining out to first base
一直線[icchokusen] straight line
鉛直[enchoku] perpendicular

下駄直し[getanaoshi] repairing clogs
開き直る[hirakinaoru] to become defiant
気を取り直す[kiwotorinaosu] to completely rethink
急転直下[kyuutenchokka] suddenly and precipitately
居直る[inaoru] to sit up properly straight