一弦琴[ichigenkin] single-stringed Japanese zither
琴線[kinsen] heartstrings
三角琴[sankakugoto] trigon (a musical instrument)
手風琴[tefuukin] accordion
心の琴線[kokoronokinsen] heartstrings

たて琴[tategoto] harp
風琴[fuukin] organ
木琴[mokkin] xylophone
提琴[teikin] tiqin (2 or 4-stringed Chinese instrument played with a bow)

琴瑟相和す[kinshitsuaiwasu] to be happily married
琴瑟相和[kinshitsusouwa] pair of persons (especially a married couple) being intimate and harmonious

琴瑟[kinshitsu] qin and se (two different kinds of Chinese zither)