This clip on tuner works through vibration. Simply clip the TGI81 onto the headstock of your guitar, bass, violin or Ukulele C. It works on a pivot system that can freely move to get your desired angle. Switch the TGI 81 Clip On Tuner with a small rubber button at the rear. The screen then lights up. When you play a note on on your instrument it will tell you if your are sharp or flat. You can then tune accordingly.