Bowstring
げん
つる
None
The mysterious sound that comes from a bowstring when you pluck it is called a chord. It's still a bowstring though. You need strings to make chords, after all.
The chord you're hearing right now is being played by Genji (げん). He's sitting under your window plucking bowstrings and singing.
Currently there are no similar looking kanji which exist in the WaniKani learning system