This site is dedicated to everyone interested in Serge Modular Music Synthesizers
Review in Keyboard magazine, by Dominic Milano, July 1981

MODULAR SYNTHESIZERS hold a somewhat special place in the hearts of many a synthesist. Most of us would like to own one someday. They're a status symbol, and they're fun. But they're also intimidating --the front panel looks confusing, they're big and cumbersome, and they're impossible to use live unless you've got the bucks to put in some fancy interfacing for computer control. At least that's the popular myth. But there are a few companies brave enough to ignore the myth and offer modular instruments to the public.

Still, the beasts that were the forerunners of today's cut-down, performance-oriented synthesizers have become the exception and not the rule. As pushbutton instruments have become the rule, modular synthesizers have declined in popularity. Only a few companies are still making modular analog systems in the conviction that they are indeed musically useful. One such company is Serge Modular.

The Serge system is a little confusing at first, even if you're used to working with other modular systems. The confusion stems not only from the fact that Serge uses unfamiliar terms for some familiar functions, but from the fact that many of the modules don't perform single specific functions; rather, they're "patch-programmable," which means that they do different things depending on how they're patched up. This design allows Serge to put a lot of capabilities into a very small space. It also gives a small system a kind of flexibility that you'd expect to find only on the biggest modular systems.

The system we had to look at was the last of the standard configuration of modules known as the Series 79 Serge system. The Series 79 is being discontinued, although all of the individual modules in the system are still being offered. So what we will offer in this column is really more an overview of what you can put into a Serge system than a review of a particular system, since the idea behind a modular system is that you can put whatever modules you need into it in whatever numbers you need.

Patching
Interconnection between inputs and outputs on the various modules is done with unshielded banana plugs. The Buchla modular system also uses these, and to our mind there's a very logical reason. Banana plugs are made with both male and female jacks at both ends, so you can plug one cord directly into another, stacking as many as you like into one panel jack. So you don't need to fill up a lot of space with multiples. The patch cords offered by Serge are made by ITT, and come in packs of 10, each pack containing an assortment of lengths. The cords are color-coded by length. They're unshielded, but the output impedance of each module's output is low enough to allow the Serge folks to get away with unshielded cords. We did hear some bleed-through and crosstalk between input and output in a few isolated cases, but it wasn't so bad a problem that you couldn't live with it.

Sound sources
There are a number of modules, including the Dual Transient Generator and the Smooth Function Generator, that can be patch-programmed to act as VCOs, but the basic VCOs made by Serge are their New Timbral Oscillator (NTO) and their Precision VCO (PCO). They also make a noise source.The NTO has some really useful features that you won't find in oscillators every day. There is a voltage-controllable variable waveform, a voltage-controlled portamento function, and both linear and exponential control voltage inputs. The linear frequency modulation input lets you modulate the harmonics of a waveform without altering the fundamental, so you can get some complex and pleasing digital-sounding timbres. The range of this VCO is from below 16Hz to over 16,000Hz. With added control voltages, the range is extended from less than .1Hz to more than 100,000Hz. The output waveforms include sine, triangle, sawtooth, and variable. These are available simultaneously. There's also a sync function. a voltage processor that can attenuate and invert, and a CV input with an attenuator on it. For more traditional keyboard-oriented applications, it might have been nice to seen some provision for switching in increments of octaves, but given the emphasis of the unit on non-keyboard-oriented events, we didn't really miss it. In fact, Serge is coming out with a quantizing module that will enable you to get octaves fairly easily.

The PCOs give you sawtooth, sine, and triangle outputs. They also have the linear FM input, two 1V/octave control inputs, and an exponential control input with a voltage processor thatcan attenuate a voltage as well as invert it. Just as on the NTO, there is a sync function. The PCOs also have a high- and low-frequency range control.

Filters
Serge has four different types of filters. The filter that was on the system we had was their Variable Q VCF. Most every filter has variable Q, but this one's Q is voItage-controllable. The cutoff slope of the filter is 12dB/octave. A lot of people might scream, "Why not 24 db/octave?" They should relax, because Serge makes a filter that'll do that too. But before we jump to that, the Variable Q filter not only gives you a lowpass output but highpass, bandpass, and band reject outputs too. And that's all simultaneously! The cutoff frequency control has a positive/negative voltage processor associated with its control input. There is also an input that has an automatic gain control on it, so the filter won't overload and distort at high Q settings. If you're not using this input, you have to be careful to set the gain control just right; otherwise you'll get a lot of distortion, which you may or may not want. A separate input for trigger pulses make the filter ring whenever a pulse is received, simulating the effect of striking a resonant object.

Serge's other filters include the Variable Slope Filter, the Variable Bandwidth Filter, and the Extended Range Filter. The Variable Slope Filter is the filter that has a 24 dB/octave cutoff slope --if you want it to. You can voltage control the slope on this one (we didn't get to play with one, but the idea is fascinating). You can get as small a cutoff as 6 dB/octave all the way up to more than 24 dB/octave. There are two inputs which can be cross-faded. The Variable Bandwidth Filter has five outputs: Lowpass, highpass, variable, highband, and lowband. The high band and lowbands have fixed widths. The width of the variable width output is voltage-controllable. The Extended Range Filter is essentially the same as the Variable Q Filter, but with a second sub-audio range. The Serge people say it's useful as a control voltage processor. Like the Variable Q Filter, it has voltage-controllable resonance.

VCAs
Serge makes a whole bunch of VCA modules, some of which are just VCAs, and others of which are audio output processing modules. A few of their modules also double as VCAs when patch-programmed to do so. The audio output modules come in all kinds of configurations. There is one that's expandable from 6 to 14 channels, another that has two channels, and so on. Then there are their quad VCAs, dual cross-fader modules (voltage-controllable, of course), and something called the UPAP, short for Universal Equal Power Audio Processor. The UPAP was part of the system we had to review. It has four VCAs, VC cross-fading and panning functions, and a lot of inputs and outputs. The outputs normally run to line inputs on mixers or amps. There are standard banana plug minijacks on the systems, but we're sure you could get 1/4" phone jacks and even XLR connectors put in if you specify them when you place your order. One thing you have to watch out for with the UPAP is that when you patch a new input into it, you have to be sure to turn the volume down on the VCAs. Otherwise you may blow your eardrums out unexpectedly, because the VCAs deliver quite a gain boost.

Processor Modules
One of the neatest, most interesting modules we've seen in a long time is the Wave Multiplier module. It has three sections on it. The top section can act as a linear gain VCA, or it can be set to square up an input signal. This gives a sound similar to an over-driven tube amp. The second section provides a sweep of only the odd harmonics of an input triangle wave. It gets more complex when you put in different waveforms. And there are two inputs, so you can get effects that go a little beyond what a ring modulator will do. The bottom part of the module is a full-wave rectifier. It acts on the even harmonics. A second output on the module is squared up, so it gives the input signal a sound that's a bit like pulse width modulation. It's really hard to explain all the possibilities that this one module gives you. And it's even harder to describe all the effects you can get out of it. But it does so much to a sound timbrally that it puts to rest forever the notion that filters are the only way to dynamically vary the timbre of a waveform.

Serge also has a couple of phase shifter modules, an analog delay module that will be available sometime in the near future, and other things like a waveshaper, a ring modulator, and the like.

Sequencer
The Touch Activated Keyboard Sequencer is an analog sequencer with four rows of 16 discrete voltages. It's very versatile, one of the most versatile sequencers we've seen. There are separate outputs for each row, as well as a vertical output for joining one row after another for up to 64 stages of sequencing. There is a capacitance touch plate row (don't try to play it with your fingernails - they don't work for capacitance) that has both a keyboard trigger output and an output that they are forced by lack of space on the panel for graphics to call pressure sensitivity. Actually, the pressure isn't being sensed at all. It's simply that when you press harder on the touch plates, you supply more fingertip surface area to touch the plates, and thereby create more capacitance, which comes out as a corresponding control voltage.The touch pad keyboard has 16 steps of equal voltage. This obviously doesn't yield an equal-tempered scale, but for certain types of music, that's what you want. Add the soon-to-be-offered quantizing module and you've got your replacement for a standard keyboard.

The sequencer will also step up and down; it can be set to hold on a stage whenever an input gate is high; it can be patched to reset at any stage; the keys can be used to determine where the sequence will start (very useful for live performance); holding down a key halts the sequence at that stage until you lift your finger; and so on. You get the idea. It's a versatile device that's much more playable than the automatic bleep machines that are what most people think of when you say 'sequencer' to them.

Other Control Modules
There are quite a few control modules that are available, and we'll only touch on them briefly. There's a Dual Transient Generator (it's an AR) with voltage controllable rise and fall times, a Triple Comparator, a Triple Bi-Directional Router, a Random Voltage Generator, a Dual Random Voltage Generator, an Analog Shift Register, a Dual Analog Shift Register, a Dual Voltage Processor which you can use to invert and attenuate waveforms, and a DADSR module with voltage-controllable segments.

And now we come to the confusing but fun modules. There's one called the Smooth and Stepped Function Generator. This one is patch-programmable. Among the things it can be patched up to act as are: a LFO with a triangle output, a portamento device, a complex staircase wave generator, a sample-and-hoId, and so on. It's a confusing module. It took us a few days to feel comfortable using it (the pre-publication owner's manual had some mistakes in it that made things even more confusing) but it did quite a lot for a single module. The one we had to look at had a slight defect in it. With only one patch cord in the entire system, going between the input and the cycle output of this module, and no other patch cord even connecting it to the output module, you could still hear the Smooth Function Generator oscillating faintly in the distance.

The other patch-programmable multi-function module that we haven't talked about yet is the Dual Universal Slope Generator. This module can be patch-programmed to do even more things than the Smooth and Stepped Function Generator, but it wasn't nearly as confusing to use. It can function as a voltage-controlled LFO with a triangle output, a voltage-controlled portamento device, an envelope follower, a voltage-controlled pulse and trigger generator, a voltage-controlled pulse delay, a subharmonic series generator, an audio oscillator with sawtooth and triangle outputs, or a non-linear lowpass filter which is fairly primitive and low-fidelity, but that does work nonetheless. The Slope Generator has, among other goodies, a trigger output that fires when the Generator reaches the end of its cycle. This can be used to trigger another Slope Generator, and the outputs from any number of Generators can then be mixed to create much more complex envelopes than are available from any ADSR.

Conclusions
While all instruments are limited in some ways, the Serge synthesizer is less limited in its capabilities than the typical synthesizer. The bottom line for any instrument is whether it has a good sound. The answer to that is that the Serge sounded very acoustic and natural in many settings, and not so acoustic and not so unelectronic in others. It really depends on what you do with it. Some of the sounds we got out of it were so vocal sounding that it seemed uncanny. Fat bass sounds? Well, the particular system we had didn't lend itself to doing that kind of thing. Remember that it didn't have a keyboard on it (Serge doesn't even make one, though their 1V/octave control voltage inputs allow you to interface easily with most any synthesizer keyboard).

The Serge system is one system that those who are tired of the etched-in-stone, this-is-a-synthesizer synthesizer should look into. It does a great job at challenging you to use it as an instrument and not just as a noise machine to do gargling goose noises, although it does those really well too (don't all modular machines?). The challenge with any synthesizer is in learning to play whatever instrument you've set it up to be, and the Serge can certainly be a lot of interesting instruments. If you do decide you want to order a Serge instrument, remember that you don't have to limit yourself to the lineup of modules found on a typical synthesizer. Maybe you'd rather have ten oscillators, or five filters…

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