A device for instantly lengthening a support strap on a guitar depending on the players mode of playing and the rhythm of the tune. The device consists of a base plate which has the strap trained therein and is carried on a player's upper body. The base plate has at a lower end thereof a hinge which a movable counter plate thereto. The movable counter plate has a multiple of openings thereon through which a guitar strap can be threaded at predetermined locations. When the movable counter plate is in an up position it is arrested at that location and the guitar strap is doubled back upon itself. When the tune or the rhythm thereof requires a change in beat, the movable counter plate can instantly be released to assume a straight down position, whereby the strap is lengthened and the guitar can be played at a lower position of the body of the player.