A body adapter for a stringed musical instrument, comprising: a bottom portion and a varying thickness perimeter sidewall portion, where a space bounded by the bottom portion and an inside portion of the perimeter sidewall portion, forms a receiving compartment. The receiving compartment has a shape adapted to releasably receive the body of a stringed musical instrument and thereby change the shape of the instrument as it is held by a user for playing, from that of the outside shape of the musical instrument, to the outside shape of the body adapter.