An apparatus and method for extending and retracting frets of stringed musical instruments such as a guitar or bass guitar. Each of a plurality of frets is an integral part of a fret-cylinder having an axis oriented approximately perpendicular to the direction of the strings when positioned in a neck of the instrument. Each fret-cylinder has integral cylinder-adjusting teeth that engage rod-adjusting teeth of a rod enclosed within a cavity in the neck of the instrument. Moving the rod in an axial direction by a rod actuating mechanism causes the fret-cylinders to rotate about their axis, extending the frets above a fingerboard attached to the instrument neck for fretted play and retracting the frets flush with the fingerboard for unfretted play. The rod actuating mechanism may be positioned on a neck of an instrument or a body of an instrument, and may be manually or electric motor actuated.