In music performance and education, thumb position, not a traditional position, is a string instrument playing technique used to facilitate playing in the upper register of the double bass, cello, and related instruments, such as the electric upright bass. To play passages in this register, the player shifts their hand out from behind the neck and curves the hand, using the side of the thumb to press down the string; in effect, the side of the thumb becomes a movable nut (capo).