The kanji 曲 looks like something bent out of shape, like a twisted piece of wire or a paperclip that has been deliberately curved. Visualize the square in the middle being the 'original' shape, now distorted.
'Kyoku' — sounds like 'crooked', which is a type of bend or curve, and also relates to something not straight or honest (a 'crooked' deal). This can help with both the 'bend' and 'song' meanings, as a melody often has a winding, 'crooked' path.