“Realistic Moog Concertmate MG-1 Analog Synthesizer with MIDI Control, Filter Input, Improved Response
Information
This listing is for a unique Realistic Moog Concertmate MG-1 that has been modified and now has MIDI input and control, filter audio input, and improved retrigger speed and glide response. Here is a list of all modifications:
Sticky black foam removed
1/4″ Audio jacks for input and output (see photos below)
External audio input to filter (see photos below)
Improved gate response
Multitrigger & continuous glide
Octave pitch drop
MIDI2CV – Design: Bojan Burkeljc
Notes – CV/Gate
Velocity – Filter Cutoff Frequency CV
MIDI CC#1 – Filter Cutoff Frequency CV
MIDI CC#2 – Oscillator 1 – Pulse Width (~25-50% Duty Cycle)
MIDI CC#3 – Oscillator 2 – Pulse Width (~10-35% Duty Cycle)
CV/Gate (From MIDI or Keyboard) Select switch
Cosmetically, the MG-1 is in very good shape. The case is in excellent condition for its age, but the keys have some scuffs and rough patches. There is one slide cap missing and some are slightly loose.
These modifications transform the existing MG-1 into an expressive, responsive, and controllable analog monosynth with a lush Moog ladder-filter. One of the first things I noticed when playing this MG-1 with a MIDI controller was how dynamic it felt. The filter really opened up when I played heavy-handed, and became smooth and dark when I played lightly. I then used MIDI software to generate and apply MIDI CC LFOs to the pulse width of both oscillators and then it started getting complex… The pulse width modulation isn’t over-the-top, it stays within a range that adds character but preserves the overall Moog sound. With the MIDI LFOs running, I turned up the MG-1′s internal modulation routing and that resulting sound easily surpassed the original MG-1, it reminded my of playing a Mono/Poly or a Pro One. On top of that, you can add a MIDI LFO or the internal modulation to the filter cutoff.
To the left of the keyboard, there is a switch to select between MIDI keyboard control or internal keyboard control.
The MIDI input is by far the biggest upgrade to this MG-1 – with this interface you can control the notes, the filter cutoff, pulse width of oscillator one, and pulse width of oscillator two. In addition, the midi note-velocity controls the filter cutoff. Both the filter input and the MG-1 output are 1/4″ jacks (they take the place of the cv/gate in). The MIDI board is a MIDI2CV, designed by Bojan Burkeljc. The board converts MIDI data from note on/off messages to pitch and gate voltages, velocity to filter cutoff voltage, cc#1 to filter cutoff voltage, cc#2 to pulse width cv for oscillator 1, and cc#3 to pulse width cv for oscillator 2.
The sticky black foam has been removed from the MG-1.
The filter input and MG-1 output use the existing 1/4″ pitch and trig jacks on the back panel (see photos below). The jacks are unlabeled in order to preserve the original aesthetics as best as possible.
The external audio filter input can be mixed with the other signals, since it enters the circuit in the mix section behind a resistor.
The improved gate response affects the keyboard gate and allows for faster internal keyboard playing (quicker successions of triggered notes)
The multitrigger modification affects play of the internal keyboard. It restores Moog’s typical low-note priority, retriggers when you play a new note and release a note to return to the original note. It also adds continuous glide, such that the glide will not stop in-between notes (and off-pitch) if you take your hands off the keys, the pitch will continue to glide to the note you played.
The output sounds best with the volume somewhere in the middle. You can turn it up to full volume to get interesting overdrive effects. ” Link
“The MG-1 is a 2-VCO monophonic/polyphonic analog synth built by Moog Music and was sold through Radio Shack Stores. 
