Adam's guitar was a musical instrument used in the 23rd and 24th centuries. Adam played a six-stringed instrument, similar to a guitar but without the resonating body. (TOS: "The Way to Eden" ) A similar instrument was played by the Edo on Rubicun III and by Katie aboard the Enterprise-D; her instrument had eighteen strings, however. (TNG: "Justice" , "When The Bough Breaks" )