Abstract: A tuning device for a stringed musical instrument consisting of stroboscopic light sources, such as light emitting diodes (LEDs), positioned to be seen by a musician in or near normal playing position as partially eclipsed by the strings. The LEDs are driven at standard musical frequencies by a microprocessor. To use the device, a musician observes the illusion of a moving shadow around an untuned vibrating string, and adjusts the instrument until the shadow appears to slow down and stop. The LEDs are sufficiently powerful, and their duty cycles are sufficiently large, that no special shielding or means of observation are required by the musician in normal ambient lighting conditions. A plurality of LEDs is grouped behind each string, with each LED in the group having the same frequency but different phase, which creates an illusion of movement along the string in one direction or the other indicating whether the string is sharp or flat.