Abstract: A transposition device that can be applied with one hand to the neck of a string instrument provides continuously adjustable pressure to adjust the musical sound of a string and includes a frame with a yoke and a first arm extending from one end of the yoke. A movable second arm is attached to the opposite end of the yoke by a first pivot. The second arm includes a cam follower and a compliant material on an inner surface. A cam movably attached to the frame by a second pivot contacts the cam follower of the second arm. When the cam moves from a first position to a second position, the second arm moves from a disengaged position to an engaged position that presses a string of a string instrument with a continuously adjustable pressure. The user selects the pressure desired while the capo is being installed on the neck of the string instrument. The cam may be exposed or it may be enclosed by a portion of the frame.