The Motor Synth MkII from Gamechanger Audio is, by some margin, the most original synthesizer design I've seen (and heard!) in some time. It's a desktop unit that generates audio waveforms via its eight variable-speed internal drone motors – that's "drone" as in UAS/UAV/quadcopter. As its eight brushless DC motors spin inside the MkII’s sturdy metal enclosure, they deliver two separate voices with three types of optically generated waveshapes each (sine, saw, and square), plus a fourth "electromagnetic inductive" waveshape that uses eight magnetic pickups instead of the optical sensors (similar to a tonewheel organ). A third digital voice is available (DCO), providing a total of three voices that can be mixed in five different octave ranges each.
There's analog filtering, Drive, and digital modulation, as you'd find on many synths, and a healthy breadth of up to seven envelope types for amplitude, filters, or modulation. The DCO uses a separate digital multimode filter that conveniently shares the same controls as the analog filter section with the press of a button on the well-designed front panel. You can feed external audio into the synth as a carrier signal to trigger the built-in sequencer, act as an envelope follower, or use the Motor Synth MkII as a vocoder (Gamechanger advises using a preamplified mic for the vocoder input).
Nerdy bits: The sine, saw, and square waves are generated by an infrared optocoupler pair that reads three distinct graphical patterns imprinted on reflective optical discs mounted to the drone motor shafts. These patterns, located on the bottom side of the discs, represent sine, saw, and square waveforms. Higher pitches are created as the motors and discs spin faster. The Motor Synth MkII has transparent windows on the front and back, allowing you to observe the eight motor discs in action as they respond to your playing and patch changes in real time – much like the hot rod with the transparent hood in the original Grease film! The MkII is capable of playing notes either in unison (four motors per note per voice) or playing up to four notes of paraphony (there is a single analog filter stage per voice).
The often shrill but harmonic sounds that the eight mechanical motors produce (not the synth output, mind you – I'm talking about the sound of the instrument’s mechanical workings in the room) are fascinating enough that I found myself frequently recording them with contact mics. It's like a tiny, reactive, spinning choir of birds.
Cooling the Motor Synth MkII’s eight motors requires a fair amount of active ventilation, so a relatively high-powered fan is included in the unit, pulling air up from the bottom panel vents and blowing it out the side. A special motor diagnostics section of the menu reveals that motor temps can easily reach into the 100° F+ range, so the fan is often essential. Between the ambient noise of the motors spinning at varying frequencies and the fan, the MkII isn't exactly a quiet studio instrument. When measured with a sound level meter, I found it generated about 48 dBA of ambient noise, even when not being actively played. During some patch changes, you can feel the instrument housing vibrate with the momentum and velocity of the motors (think of a car engine revving at a stop sign). There's a convenient 3.5 mm headphone jack, so the noise is no big deal for tracking solo at home. However, tracking live with the synth might require players to use a sound booth in certain setups. It's power-hungry, with an external 24V/120W power brick feeding the ravenous baby birds inside.
The Motor Synth MkII sounds impressive, with a low end that is especially rich, particularly when the 24 dB low-pass filter is engaged with a bit of added resonance. I'd characterize it as a "weighty" instrument, capable of epic and sweeping pads, nasty or wobbly vintage leads, piercing pitched plucks, and everything in between. You can apply wild ramping slew to the drone motors with the Accel and Brake knobs. The onboard sequencer is a feature-rich beast, and the mod / cross-mod options are plentiful. Almost every setting is accessible via the crisp OLED menu, and there are several nice presets.
I did hear some high end aliasing on specific sounds. I used the spectrogram in iZotope RX [Tape Op #164] to help confirm that what I was hearing matched the visual characteristic of aliasing (lines moving downward in the graph as the pitch goes up). I asked Gamechanger Audio about this, and they said, "This could be either due to envelopes being digitally controlled or some bleed from the motor control block. In this respect, the unit that you have is not faulty, and the deviations are within the norm, given the mechanics." Overall, the aliasing wasn't a huge detractor for me, given the general "shredded" tonal character present in many sounds I patched.
Beyond the unique tonal quality of the drone-motor sound sources, there are plenty of other cool and distinctive features I enjoyed discovering over time, such as the two separate send/return pairs for the two analog motor voices, allowing you to patch in effects before the filter; an advanced motion-recording knob automation feature with the ability to record automation to most front panel controls, then change the speed of the automation playback lanes independently, MIDI sync any of them; using the internal clock to keep everything lined up to your subdivision of choice; a performance interface feature that lets you assign pitches, scales, or parameter locks to the eight panel buttons for instant recall; or the Clutch key, which, true to its name, acts as a buffered recall macro effect: Hold it down, manipulate multiple knobs, then release the button to “pop the clutch” and engage all of the settings changes you just made. The Clutch feature can be hit or miss, but when applied to elements like the filter cutoff or the Accel/Brake knobs, it leads to some wild transitions.
During my first attempt at booting the Motor Synth MKII, I encountered a minor issue with the SD card formatting, which the support team at Gamechanger Audio quickly helped resolve. Even though it has recently dropped in price, the cost of the MkII sets it well outside the range of the average impulse buy for sure, but again, this is unlike any other instrument in your studio. So, for the adventurous studio motorists out there who are looking for cinematic sounds, I recommend this Sunday drive – just bring a pair of headphones.