Abstract: This invention provides a control system for automatically tuning a stringed musical instrument, utilizing a library of calibration functions to tune the instrument in a plurality of operating conditions without recalibration. The operating conditions can include changes in temperature and humidity, different sets of strings made with different materials and gauges, broken strings and the installation of a capo. Calibrations can also be provided for instruments of different makes and models, string lengths, body materials and actuator types. The control system is adapted for use in a stringed instrument having actuators attached to each string for changing the frequency of the string in response to a control signal. Each calibration function relates the frequency of a string to the actuator position of that string. The invention further provides an automatically tuned stringed instrument using the control system, and a method for tuning a stringed instrument.