Abstract: A microtonal musical instrument interface device between one or more Musical Instrument Digital Interface (MIDI) controllers and one or more musical instruments comprises a housing and a plurality of potentiometers on a surface of the housing. The potentiometers comprise twelve tuning potentiometers constructed and arranged to correspond to notes of a musical scale, each tuning knob for tuning one of the notes; an offset potentiometer for globally tuning all of the notes by a same amount; and a range potentiometer for setting a maximum tuning range of the tuning potentiometers. A microprocessor in the housing modifies a MIDI data stream received from the one or more MIDI controllers for output to the one or more musical instruments according to a position of the potentiometers.