The head tune is a clip-on tuner with a unique design that"s based on the shape of a guitar, bass, or ukulele headstock. With the head tune attached to the headstock of an instrument, play a single note on the string that needs to be tuned. Two indicators will illuminate: the string indicator LED will show the peg position, and the LED meter will indicate the tuning of that note. This makes it obvious which peg needs to be adjusted. There are four models: two models that are suitable for guitar headstocks, a model for bass, and a model for ukulele.