A musical instrument string winder designed for faster tightening or loosening of a guitar key or similar that utilizes a planetary gear drive includes a handle housing with a protruding key socket near its periphery to accept a guitar key. The key socket has a recess for engaging a guitar key on one end and an integral planet gear on another end. The handle has a gripping portion one end and a relatively large integral ring gear on another end. The key socket planet gear has a predetermined diameter which is notably less than the diameter of the ring gear to afford it orbital movement around the ring gear. The key socket planet gear rotates on its own axis, subject to its position along the ring gear and is mated to a connecting element that is rotatably mounted to the center of the handle housing. Thus when the guitar key and key socket planet gear are engaged and the handle housing is held steadfast while being moved in a cyclic motion generated from the elbow in an arc defined by the ring gear, the planet gear is urged to track along an orbit defined by the ring gear, resulting in more than one rotation of the musical instrument key for each cycle of the handle. Other embodiments are described and shown.