Behringer Poly D Synthesizer

Today we are taking another side trip down yet another obscure road I’ve traveled as a guitarist and musician. Lately I’ve been building up the tools I need for scoring and music sessions. I've also been gearing up to record a pair of musical pieces I wrote way back between 1978 and 1981. In order to get them right I needed some keyboard sounds that were in my mind when I wote them. After seeing some videos of modern Alt Folk groups during the lockdown I came across the harmonium with its rich timbre and thought, “Hey this is cool! It could fill the corners.” But as I got ready to purchase one, the company I was dealing with ran into problems with supply. Covid strikes again! So there I sat with a bit of cash in my pocket when suddenly I sort of stumbled across the instrument that is the subject of this review through a bit of nostalgic browsing. Oh, maybe a certain amount of impetus came from the recent Moog Music newsletters that I always read. Why? Because I love synthesizers!

Rick Wakeman with a pair of MiniMoogs on top of Mellotrons

My first brush with synthesizers was way back in the analog days. At the dawn of the 1970s, synthesizers burst into rock music for the first time. Rick Wakeman of YES and Peter Bardens of Camel pioneered the use of the MiniMoog, Keith Emerson played a full-sized Moog modular system, and Edgar Winters, Joe Walsh, and Pete Townsend played Arp Synths. Throughout the early and mid-70s, players were coming out with fresh, brand new sounds that they made with synthesizers. That time of innovation was an extremely exciting period in music. I remember Keith Emerson’s work with Emerson, Lake, and Palmer, was the first to hit the radio with the 1970 song, “Lucky Man,” which was the very first outing of the Moog in popular music.

Then in 1972, YES released their magnum opus, Close to the Edge, which was liberally seasoned by Rick Wakeman’s synth work. The next year Rick released of his first solo album, The Six Wives of Henry VIII, featuring a huge battery of keyboards including a pair of MiniMoogs. Years later he is still using his original MiniMoog Model Ds from the ‘70s. Check out this video of his solo section in a 2003 YES concert. You can see him use the MiniMoog as the bass end of his pipe organ sound, starting at 3:58. The video's initial freeze frame features that section of the solo, exactly:

But back then, everyone was getting into the act. This 1973 Joe Walsh and Barnstorm song is full of synth bass, accents, and sound effects:

Then in 1978, my band needed an intro for the beginning of their second set. I took in a portable tape recorder to a local guitar store and spent an afternoon with a Moog Sonic Six suitcase synth, building a rudimentary piece that worked out great for us. From that moment on I was hooked. A year later I decided to study music composition and recording techniques at the University of Tennessee. The professor who taught tose subjects also taught electronic music and electronic music composition and operated a studio at the school. I hopped on for a ride and was soon up to my eyeballs in large scale synthesis, utilizing their many units including the Arp 2600, EML Electrocomp 101, EML 400/401 sequencer, and Synthi-A. We were introduced to the Synclavier II as well, which was at that point the premier digital FM synthesizer and sampler. I wrote several electronic pieces which were premiered to audiences in the community. But before I finished at the school I was hired away to a career in audio-for-film-and-video which led to my becoming a sound designer. Well that’s me. In case you care.

But let’s back up a touch and look at the beginnings of portable synthesis. At their birth in the period of 1960-1970, synthesizers were modular and analog. By modular I mean that each function was offered by the synth makers as a separate, discreetly-wired electronic module. You placed your collection of modules in large racks and patched between them. These rack units were huge, heavy collections of hand-wired things that could fill a wall or a small room. They were obviously not at all portable so studios were often built around them. Operation required a thatch of multiple patch cables running back and forth, to set up a “patch” or basic sound. There were no polyphonic synthesizers at the beginning, so recording any sort of chordal or polyphonic passages involved laying down multiple recording passes in the studio. Because these instruments were also highly unstable, subject to pitch fluctuation from minute temperature changes, multi-tracking often took days of recording while retuning the unstable oscillators between each take. Then in 1969, while on his lunch breaks, Moog engineer Bill Hemsath toyed with creating a smaller, self-contained synthesizer. He wanted to somehow come up with a unit that offered most of the modular systems’ capabilities in a small package that would be easier to use and portable. Bill’s attic office contained the company’s junk pile of discarded modules that Bob Moog hoped to find another use for. In the pile was the remainder of a keyboard Bob Moog had cannibalized for keys.

The Moog Model A

After Bill hacksawed off the scavenged portion of the keyboard, the forty-four remaining keys determined the horizontal width of his prototype unit. Hemsath built a case to contain the keyboard and from there it came down to how many modules could be fit behind those keys on a control panel. The “Moog Model A” prototype was born.

Whence It Came - Courtesy the Audities Foundation

A year later, after three more prototypes, Moog debuted a quite portable package with preset routing that weighed only thirty-two pounds, the MiniMoog Model D. The MiniMoog Model D sported three oscillators that could be independently tuned and stacked and a unique four-pole, 24db-per-octave “ladder” voltage controlled filter that soon gave it a reputation amongst musicians as a full, fat sounding synth. It was still one-key-at-a-time monophonic and still had thermal oscillator drift problems but the tremendous reduction in weight and size and a folding control panel made it far more practical to transport than any previous synthesizer. Moog also came up with the now-familiar two-wheel pitch and mod control section to the left of the keyboard for the Model D that has gone on to be the standard in the industry. Walnut cabinetry made it aesthetically pleasing as well. The price? A mere $1600 in 1974, which amounts to $8900 in today’s money. Surprise! A good example from the period still commands that price. This was considered the first "musician's synthesizer" and many consider it the most popular synthesizer of all time.

In All Its Glory: The MiniMoog Model D

Twelve thousand examples of the Model D were built in three phases between 1970 to 1981. Along the way, aftermarket companies came up with oscillator modifications that made the unit far more stable. During that time, competitor ARP came out with their similar Odyssey mini synth with its duophonic (two pitch) capability and a brighter sound and features that allowed owners to explored some other tone-generating capabilities as well. Still, no chording was available. Polyphonic synths finally arrived at the end of the 1970s, spelling the end of the MiniMoog, but they never tied together the flexibility, immediacy, and "phat" sound of the Mini Moog with their polyphony.

Meanwhile in the early part of my career, early in the 1980s I began being called upon to create sound effects and to score music for film and video. I picked up a rudimentary 1970s MiniKorg 700 monophonic analog synth in a trade but it was never complex enough for most of my work. I added a guitar synth with polyphonic and multi-timbral capabilities, but I really needed the capabilities of at least a three-oscillator analog synth like the Model D. Fast-forward to recent days when I watched the MiniMoog being resurrected by Moog, Inc. for two years starting in 2016. Some new features were added and the unit was given a price tag of about $3500, but it was still monophonic.

By the way, here is a useful aside: For years I have pronounced Bob Moog’s last name as if it were "Mow-g" with a long "o". At this point I’ve spent a lifetime being corrected about this by a faction that believes that it should be pronounced moo-g, like the bellow of a complicated cow. They are wrong, as are most people who try to pronounce my last name. Here is the man himself on the subject:

That brings us to the next step in the life of the MiniMoog. German manufacturer Behringer has always had something of a, um… shall we say, pirate reputation. They love to look around for ways to backwards-engineer popular audio equipment and offer it at far more affordable prices than those of the original gear. The folks at Behringer recently discovered a fondness amongst musicians for the old synths that made the recordings of the 1970s and ‘80s, synths that had been too expensive to be purchased as a secondary instrument. They found that the patents behind these synthesizers had lapsed over time, so their staff tackled the job of backwards-engineering some of them. This led to their recent release of a raft of synth clones that they are offering at an average of one-fifth of their original prices. To whit, in 2018, Behringer introduce their tiny Model D, a miniaturized, keyboardless, full-featured Eurorack version of the MiniMoog with MIDI keyboard control, offered at a price point of $300. A user could add a cheap MIDI keyboard and have a MiniMoog. BAM! The Model D flew off the shelves like hotcakes. Next, they put out an exciting version of the ARP Odyssey with several upgrades. Finally, early in 2020, came the subject of this article, the Behringer Poly D.

The Behringer Poly D. Click for Larger Pic.

The Poly D is a portable, modular, self-contained, integrated, analog synthesizer with a completely analog signal path. The voltage control path is also completely analog. It is controlled by you - your hands control everything, so the experience is extremely interactive and immediate, as an analog synth should be. There are no presets per se. It is a paraphonic synthesizer, meaning that its four oscillators can be played simultaneously through a single ADSR volume envelope and a single filter envelope.

The Poly D carries the basic MiniMoog Model D Form factor and control logic. The visual aesthetic includes the MiniMoog’s layout, the tilting control panel, the knob style, and the colored rocker switches. Other aesthetic nods include the wooden mini-fallboard and cheek boards in the same color as those of the MiniMoog. The wooden key slip and buffer panel at the top of the control panel have been omitted and the mod wheel panel is now all metal to save space. The wood used appears to be fruitwood or some such rather than the original walnut, but it is very nicely finished. The Poly D features substantial, rugged construction with an aluminum frame and box. The control panel pivots on a full-length piano hinge. The unit is smaller than the MiniMoog by approximately three inches each direction and weighs a corresponding nine pounds less. However, at twenty-three pounds it holds down the end of a table rather well. Part of the way Behringer achieved this was to move the power supply outboard into a proprietary wall wart. And yes, other reviews are correct: the cord between the wart and the synth is a tad short. Plug the wart into a cheap two-conductor zip cord as an extender and you are fine. Though the keyboard has thirty-seven keys rather than the Mini’s forty-one, it is a substantial, non-weighted, full-sized, Hammond Organ-style keyboard.

The Poly D reproduces the classic Moog four-pole, 24db-per-octave “ladder” voltage-controlled filter (VCF) and the classic Moog voltage-controlled oscillators (VCOs). It also reproduces the Mini’s three-knob ADSR systems, one each for loudness (VCA) and filter (VCF). The Poly D reproduces the unique ADSR “release” control of the MiniMoog: the release function for both of these ADSRs is enabled by a single “Delay” switch, in this version moved up onto the control panel, that applies the “Decay” setting to both the filter and VCA release phases when switched on. The old external input trick from MiniMoog days works as well: you can patch from the headphone out to the external in and add that signal in to push the filters more quickly into feedback and to add a touch of midrange and grit to the signal.

The Poly D has stepped up from the Mini’s three VCOs to four. To top that off, they’ve also added an independent low frequency oscillator (LFO) to the controller section offering triangle and square waves, so you don’t have to lose a VCO from the tone stack if you wish to a little vibrato or modulation. The new VCO oscillator #4 is a wide range unit that offers a pure triangle wave shape the other VCOs don’t. It can be routed as an LFO or VCO modulation source to both oscillators and VCF. As VCO #3 was on the Mini, VCO #4 on the Poly D can be disconnected from keyboard tracking if you desire. The Poly D expands on the Mini’s modulation routing to allow the added Mod sources to be routed to the oscillators and VCF.

The paraphonic keyboard handles assignment of the oscillators in three modes: “Mono,” “Uni,” and “Poly.” “Mono” makes the keyboard behave like the original Mini, with all the oscillators tracking together and assigned to whatever single key you press. Priority is given to the last key that is depressed. When an individual key is pressed in “Uni” mode, the synth assigns all available VCOs to it. When two keys are pressed, it splits the four VCOs between them, two each. When three or four keys are pressed, it assigns a single VCO to each key. “Poly” mode assigns one VCO per key up to four and offers an optional damping mode that controls the release of individual keys to make things more manageable in certain circumstances. It appears to assign the oscillators by time priority. Because of this when in “Poly” mode, it makes sense to set all the oscillators to the same octave so that, um, unpredictable results don’t occur. A nice touch on the Poly D is lighting on the pitch and mod wheels. When either is engaged, a gentle red light is introduced to remind you that it is in the circuit. The mod wheel brightens as you add more modulation.

The Poly D allows you to switch between the Mini’s standard low-pass mode and a new high-pass VCF operation mode, allowing you to create the drippy downward sweeps heard in the break of Edgar Winter’s “Frankenstein.” Behringer has also added to the output section a stereo chorus unit based on the Roland Juno 60 chorus. The two-speeds are quite milky and fill the stereo soundstage nicely. You can also select both speeds at once, though I’m not sure what you would use that rather wobbly sound for. Behringer also added a three-knob (Distortion, Tone, Level) analog distortion circuit based upon the Boss DS-1 to the output stage for those times when the sounds seem just a little too… tame.

The Poly D also adds Behringer’s basic sequencer that can record, edit, and store eight, 32-step patterns. The sequencer also allows you to “play” it in real time, changing patterns and transposing by touching keys. The Poly D also adds an arpeggiator that allows you to capture chords, arpeggiate them, and play them back in eight different patterns. That feature will end up being quite useful for studio creatures like myself. On the keyboard control side, Behringer have also added a velocity-sensitive keyboard, a USB jack for both MIDI and computer access, five-pin DIN MIDI IN, OUT, and THRU jacks, plus 1/4" after-pressure, pitch, v-trig, and velocity output jacks, and 1/4" v-trig, loudness, filter, oscillator, and modulation, input jacks. The audio outputs of the Poly D are a pair of balanced 1/4" TRS jacks. As a matter of logic, the synth’s output is only truly stereo with the stereo chorus engaged. Behringer offers PC and Mac configuration software for the poly D that additionally offers the possibility of installing updates to the MIDI control software.

The Mini’s A-440 tone generator for tuning. You’ll have to use an external tuner.

The Mini is one of those "maid of all sessions" instruments I’ve seen hanging around in many studios for years. This incarnation really carries the flag forward for the instrument. You can use the Poly D in music to play drones, leads, chords, bass lines, pads, and patterns for songs with this synth. I connected up my Roland GR-20 guitar synth via a MIDI cable to drive the Poly D and the two talked immediately. At first the Poly D was only receiving input from one string of the guitar, but I consulted the GR-20 manual and found that all I needed to do was switch the GR-20’s MIDI output from “Mono” to “Poly” to make it transmit output from all six strings down one MIDI channel. Bam! I could play leads with stacked oscillators in Poly D Mono mode or chordal pads in Poly D Poly mode. The tracking is excellent, possibly better than that of the GR-20 itself.

I have to say that the ability to stack four oscillators makes it possible to generate some ridiculously fat sounds, and I mean ridiculously fat. You can start with a bass oscillator at 32 feet, add a pair or slightly detune mid oscillators at 16 feet for fatness, and add an 8 foot treble oscillator for definition. It is huge.

In sound design sessions the possibilities are practically endless. For instance, if I build the sound of an explosion and the client wants more bottom end, I can crank a couple of oscillators down to 32' range and slightly out of tune, add a little white noise, adjust the filter to give it impact, and voile'. I’d always wanted a MiniMoog for these chores and for creative fun around the studio but could never justify the cost of one. Behringer has nailed the character and performance of the MiniMoog and has offered the Poly D at a price that is far more palatable to me.

One sound I had always wanted to recreate was the weird, wobbly, wonderful, wah-wah electric guitar sound from the band Bread’s 1971 hit, “If.” For years I wondered how it was created and I finally discovered that it was made by playing a guitar through a MiniMoog, or two to be exact! Desiring to come up with something special, songwriter David Gates brought in what they used to call a “synthesizer programmer,” A person who knew how to get sound of a synth, to create a new sound. The technician set up a pair of MiniMoogs and David played his Fender Telecaster through them. While listening, I detected two VCF effects, one driven by a repeating LFO for the main wobbly sound and the other driven by an envelope that caused a bloom throughout the sustain of the notes that increased throughout each musical measure. Best I could tell, the bloom was triggered at the beginning of each measure by the operator striking a key.

I set out to reproduce this sound with the Poly D. I plugged a Tele into the external input and turned up the input volume. I had anticipated that I might need a preamp or direct box to bring up the Tele’s volume but there was plenty of gain available on the Poly D's input so I was able to proceed. Next, I routed the low frequency oscillator to drive the Poly D’s voltage controlled filter and pushed up the MOD wheel by the keyboard to mix in that modulation. With a little tweaking of the Cutoff Frequency and Emphasis controls I had the main wobbly sound going. Now it must be noted that voltage controlled amplifier doesn’t open up until you press a key. You can bypass that by using an expression pedal to control the loudness envelope. Next, I added in the VCF’s ADSR to its mod sources so that the bloom was added to the wobble. The bloom didn’t feel quite as powerful as I would have preferred so I figured I could give it more emphasis if I did it like the original with to two synths, or possibly with three recording passes. Record your guitar onto a DAW track. Play it back through the Poly D set up for the wobble and record that, triggering the volume envelope at the beginning of each measure by pressing a key. Then play back that wobble track into the Poly D with the ADSR as the VCF mod source and once again trigger the synth at the beginning of each measure to get the ADSR bloom sound. Add a little reverb to this track and you are in!

Are there donwsides to the Poly D? How about competition from other very affordable models made by the same manufacterer? Right about at the same time as the Poly D came out Behringer also offered a new ARP Odyssey clone, making the choice difficult. Were that not enough, they have just released a rack mount ARP 2600 clone at the ridiculous price of $599. Each of these synths has its own strengths and attractions but at these prices it is easy enough to pick up a couple to cover the various capabilities they each offer. Hoo, boy!

Soooo… As you'd expect, in the first few days I owned the Poly D I spent a good deal of time mucking aboot with the new synth and getting acquainted. One day in my slack moments after a session I threw together a little one-minute “proof of concept” recording exploiting its features, just for fun. All sounds except the hi-hat, cymbal swells, and finger cymbals were created on the Poly D. My utterly rustic keyboard skills are easily surpassed by my digital editing skills, but it is still a little rough. This little piece is called SUNDAY JAUNT.

That Thump:
The moment this synth dropped, unboxing and review videos showed up on YouTube. One of the first complaints was about a thump in the VCA when the attack or decay time is set short. That thump on the VCA is a characteristic of genuine analog VCAs. If you demand that they rise or fall too quickly, they thump. Back in the day there were two design philosophies in VCA control: Some design engineers eliminated the thump by setting the range of the control to where that too-fast speed simply couldn’t be called for. Others left it in and allowed the end user to choose how close he wanted to get to it and whether he wanted to use it in a sound. The former risked losing some control travel as the analog components drifted over time. The latter meant you had to adjust it out (if you chose to) but gave you every little bit of control. Virtually all of the analog synths I played in the ‘70s exhibited "the thump." The Arps did it, the ElectroComps did it, and the Moogs did it. In fact, the very first commercially available voltage-controlled gates, the Allison Research Keypex gates did it. Does anyone remember the Keypex "zipper" sound when you cranked the response times so fast that each of the ladder gain stages thumped? The design philosophy used most often was to set the response time range short enough to allow the thumps and trust operator to prevent it so that component drift over time didn't gobble up part of the useful range. It was only later when we began seeing Digitally Controlled Amplifiers (DCAs) and later wholly digital simulations that we experienced thump-free performance. But in genuine VCAs that thump is authentic. I get the feeling that this complaint in the YouTube reviews may reveal those who were actually there, back in the day, and those who weren't.

Output Level: Another repeated complaint is that the Poly D has low output level. People seem to have a problem understanding that the original Mini offered an unbalanced line level out and used a 1/4" guitar cord but the Poly D offers a balanced line level out and needs a balanced TRS 1/4" cable to get full volume out. The Poly D level will be at +4db line level if you plug in with a balanced TRS cable, but with a mono guitar cord will give you only one-half of the balanced signal at -10db, the same level as consumer audio equipment. Best I can tell, YouTube reviewers seem to universally plug in both the Mini and Poly D unbalanced with guitar cords and simply don’t understand the difference. With a balanced cable into a Focusrite Scarlett interface and both the Poly D and Scarlett set at about one o’clock, you’ve got plenty of level.

Manual? What manual?: This one may have been a function of the early deliveries, but all the unboxing videos I saw showed guys opening up their Poly D and emptying out everything but there was no owner's manual. Six months later mine came with a decent, printed manual. My only complaint was that rather that grouping all the operational sections together in each language, they broke the manual into sections and grouped all the languages together for each section. Huh? It means a lot of flipping around.

I am thoroughly impressed with the performance and quality of the Poly D. In Mono mode the extra VCO adds girth to the already full MiniMoog sound and in Poly mode you can also play pads in one pass. It doesn’t hurt that Behringer has made it so physically attractive and robust as well. I consider the Poly D a great investment and a fantastic instrument. It is a whale of a lot of fun as well! If you've wanted a Moog Mini Model D and could never afford one, here's your chance.

Behringer Poly D
Street Price $689.20
Weight: 23 pounds
Size: 25.47 x 3.5 x 14.17” (W x H x D)

For comparison, MiniMoog Model D (2016)
Price (now-discontinued): $3500
Weight: 32 pounds
Size: 28.6 x 6.0 x 17.1 " (W x H x D)