Abstract: A stringed musical instrument is disclosed having a resonating diaphragm mounted within the instrument body and carrying a bridge assembly which supports the strings so that the diaphragm vibrates in accordance with string motion to produce an improved tone. The diaphragm is mounted within the instrument in a novel and improved manner to facilitate construction of the instrument, and an improved bridge assembly structure is disclosed. Means are provided to adjust the pressure of the strings on the bridge assembly to prevent damage to the diaphragm and to obtain an improved tone quality. The improved diaphragm support structure, bridge assembly and string pressure regulating means are adaptable to a variety of instrument types and shapes.