An apparatus and method of varying the tonal aspects of a string instrument such as an acoustic or electric guitar is disclosed. The apparatus and method employing a unique zero fret assembly. The zero fret assembly includes an upper portion and a lower portion. The lower portion is configured to connect with a fret board, headstock or body of an instrument. The upper portion is configured to engage the lower portion. The upper portion is also configured to receive and support an instrument's strings. The upper portion is selectively movable relative to the lower portion by an operator to change the tonal nature of the instrument.