By Gino Robair
|Two oscillators in the all-analog Monotron Duo (left) mean you can fatten up the sound or create surprisingly complex timbres. Also real analog, the Monotron Delay (right) has a gritty delay effect instead of the second oscillator. Both use Korg’s classic MS series filter.
IT’S BEEN A YEAR AND A HALF SINCE WE REVIEWED THE ORIGINAL
Monotron, and I still marvel at the fact that Korg—makers of highly sophisticated
instruments—created an inexpensive, toy-size analog synth
that streets for $60. Did they realize how hackable it was when they
designed it? Did they predict fans of the legendary MS-series lowpass
filter would buy a handful to experiment with, or that some clever chap would
put the synth’s guts behind a Euro-rack panel? The pocket-size synth may be the
catalyst that reintroduces the i-generation to fat hardware sounds and the joys of
Thankfully, Korg didn’t make the mistake of replacing
the original model with a “Mk. II” that has more
bells and whistles. Instead, they added two more
instruments that complement the original: the
Monotron Delay and Monotron Duo. Packaged in
blister packs and accompanied by a one-page manual
covering all three synths, the new Monotrons
have the same form factor as the original—a threeposition
switch, five knobs, a ribbon keyboard, a
built-in speaker, an audio input, and a headphone
jack—and are powered by a pair of included AAA
batteries. From there, the new models are as sonically
different as they are physically similar.
More an effect than a synthesizer, the Delay
adds a simulated tape-style echo effect at the
end of the oscillator/LFO/lowpass filter configuration.
With controls for Time and Feedback, it
can easily go into grainy self-modulation, complete
with the pitch changes you’d expect as you
adjust the Time control—instant ’50s sci-fi and
King Tubby dub effects.
If that were all the Delay had up its sleeve, I’d
still drop $50 for it. But it also includes a synth
voice, though with only five knobs (and two of
them dedicated to the delay), some compromises
were made. The main oscillator offers a sawtooth
wave and goes from subsonic to about 4kHz.
The LFO modulates the oscillator and has
selectable triangle and square waveforms. A
recessed trim control on the rear panel changes
the duty cycle/shape of the selected LFO waveform.
The Rate knob controls the pitch of the
LFO—from one cycle every 50 seconds to the
audio range. The “Int” knob controls both the
pitch of the main oscillator and the modulation
depth, but inversely: Turning “Int” clockwise
increases the LFO speed while lowering the
overall pitch range of the keyboard. The remaining
control is for filter cutoff . Although the
synth might at first seem like the least interesting
part of the Monotron Delay, it’s capable of
creating sounds that other Monotrons can’t,
specifically beepy, modular synth-like tones,
which go very well with the old-school echo.
The feedback buildup of the echo effect has an
organic quality that’s hard to resist.
The Delay is also the noisiest of the Monotrons.
It’s seriously low-fi , particularly through the internal
speaker, but that’s perfect for adding grit.
What’s special about the Duo is that it offers two
square wave oscillators, though that doesn’t mean
it’s duophonic. VCO2 can be used to create an
interval you can play up and down the keyboard in
parallel to VCO1, to fatten up the overall sound, or
as a modulator.
VCO1’s pitch ranges from D1 to just shy of A6
(two octaves above middle C). VCO2 has a wider
pitch range, going from LFO territory up to the
edge of audibility, making it perfect for modulation.
In VCO1-only mode, VCO2 is used to frequency
modulate oscillator 1 using oscillator 2’s Pitch and
Intensity controls. In VCO1+2 mode, you can set
VCO2’s pitch to whatever interval you want. Then,
as you turn VCO1’s Pitch knob, the interval between
the two oscillators remains constant.
The filter on the Duo, unlike the one on the
Delay, has a peak control and a cutoff frequency
knob. Consequently, the filter can be driven
into resonance, giving your patches extra bite.
The Duo also has a Scale button that makes it
easier to play melodic parts on the tiny ribbon
keyboard—you get chromatic, major, and natural
minor scales, plus a continuous pitch mode.
Although the internal speaker enhances the
portability of these instruments, both synths
are capable of creating sounds that rattle
their plastic housing. To fully experience their
potential, plug the Duo and Delay into external
speakers. You’ll need 3.5mm TRS cables
as two-conductor TS cables won’t give you a
One of the best features is the audio input,
which lets you run any monaural signal
through the lowpass filter, and with the Delay,
the effect as well. The filter sounds particularly
interesting on percussion, whether it’s from an
iOS drum machine, an MP3 file, or some other
source. If you have more than one Monotron,
interconnect them! I own a pair of the original
model, so I chained the four units together
with the Monotron Delay at the end—I felt
like a miniature Rick Wakeman positioned next
to my tiny Stonehenge. With three Monotrons
ahead of it, the Delay’s noise floor increased
substantially, so I dialed back its filter cutoff to
mitigate some of the hash. That gave the overall
sound a vintage vibe.
It’s hard not to like the Monotron Delay and
Duo. They’re fun to play, they sound great when
plugged into speakers or a DAW, and they even
provide an inexpensive way to introduce kids to
the joys of analog synthesis. With its scale settings
and second VCO, the Duo appeals to musicians
interested in the melodic capabilities of
these synths. The additional oscillator and filter
resonance enrich the timbral palette. Fans of
vintage and lo-fi effects will get more out of the
Delay. Besides the fun that it offers as an echo, I
enjoyed the sounds it makes on its own. At this
price, though, why not get both?
PROS Inexpensive. Classic
synth and filter sounds.
External audio input. Ultraportable.
Easy to circuit-bend.
CONS Noisy output on
Unless you’re a pianist who avoids
any instrument that uses electricity,
we can’t think of any reason not to
own every flavor of Monotron.
$70 list each | $50 street each