A joystick control (20) mounted on the body (12) of an electric guitar (11) adjacent to the customarily picked section of the strings (16) provides convenient simultaneous independent gain control of two pickup signals. A pick may be held between the thumb and first finger of the picking hand while the joystick handle assembly (23) is manipulated by any free finger or fingers of that hand. This system allows smooth, quick, easy manual selection of two independent instrument voices, alternately or simultaneously in any proportion, with minimal disturbance to the player's picking. Picking strings while varying the signals' volume levels can produce desirable timbre changes, swells, and tremolo.A waveform polarity switch (19) optionally reverses the polarity of one pickup signal. When the signals are out of phase, the change in tone of their combined voice as the joystick travels is complex.