A stringed musical instrument has a molded sound box and neck where the sound box is formed of between 20% to 60% carbon fibers, or other suitable fibers, and a polymeric resin or binder. The composition of materials utilized in the sound box is selected to increase stiffness and to control the tone of the instrument. The sound box includes an adjustable attachment mechanism having a pivot which is used to secure the neck to the sound box. The sound box includes a molded bracing structure having a plurality of braces and a molded bridge having a plurality of pockets which are used to enhance the structure for the sound box and provide a desired tone quality for the stringed instrument. The neck may include a molded neck insert and a molded fingerboard which are used to enhance the stiffness and stability of the neck.