From what folks usually view as guitar instrumentals do much for me. Seems the second it's guitar anything it won't do a thing for me as a listener. That said take something like while my Guitar Gently Weeps, whether it be Harrison doing it as a vocal tune, Vinnie Moore as a high gain hang, Thomas leeb as an acoustic Fingerstyle thing, or Birdland done by Weather Report, or Lukather or as an acoustic hang...when the harmony and melody is happening the tune is happening regardless of instrumentation.