The apparatus is a user-adjustable stringed musical instrument. A rotary joint mechanism connects an acoustic body to a movable string support assembly. The movable string support assembly is comprised of common elements of a stringed musical instrument. The rotary joint mechanism enables the orientation of the instrument strumming and fingering surfaces to be rotated relative to the transverse plane of the acoustic body. Orientation of the playing surfaces may be varied during play to achieve a more comfortable position for either the fingering hand or the strumming hand thereby improving ergonomics of the instrument.