Abstract: A stringed musical instrument including a panel provided with a plurality of playing strings extended longitudinally thereon. Tuning keys are provided at one end of the panel and one end each of the playing strings is secured thereto, while the other ends of the playing strings are operatively associated to a pitch changing device. The pitch changing device is located at the other end of the panel and comprises a plurality of individual units, one for each string carried by the musical instrument. The individual units are capable of producing a bi-directional string tension adjustment in every string associated therewith in either direction, simultaneously, or separately, to provide an increase in the tension of the string, and therefore, raise the pitch thereof, or to provide a decrease in the tension of the string, and therefore, lower the pitch thereof.