Abstract: An optical pickup system for converting the vibration of the string of a musical instrument into electrical signals, adapted to be used with a pitch calculator system. The pickup is constructed with the plane comprising the optical emitter and detector substantially parallel to the body of the musical instrument. Side walls of the optical pickup prevent the vibration of any string from interfering with the pickup for adjacent strings. The pickup uses a very narrow aperture optical emitter to maximize the signal of the noise ratio of the pickup system. A separate signal from each string is then routed to the pitch calculator circuit.