An edited version of this text also appears in
SOUND ON SOUND magazine Vol.13 No.8. June 1998

Review by Chris Carter


(see also:
Analogue Systems RS 200 review)
(see also:
Analogue Systems RS System8000 review)

If the rumours are to be believed, and according to a record company exec I had a chat with the other day they are, then a Brit Pop/guitar bands backlash is just around the corner and electronic music is the next 'big thing', just in time for the millennium. Many of you reading this mag will say that electronic music never really went away, it just got absorbed into Dance, Trance, Ambient, Electronica and all their mutant hybrid variations. Well, only time will tell.

In the meantime and if, like me, you enjoy making electronic music the old fashioned way, by patching and twiddling banks of knobs, then the Analogue Systems RS Integrator modular synthesiser is like manna from heaven, controls and sockets galore!

If you are new to modular synthesis have a quick read of the WHAT IS MODULAR SYNTHESIS ? box before you go too deeply into this review and get swamped with analogue jargon and terminology, otherwise read on.

Following a growing trend Analogue Systems have designed the RS Integrator around a standard 19" wide Eurocard Sub-Rack system, with two types available the 3U, RS10 and 6U (dual 3U), RS15. Each 3U case will hold approximately 6 or 7 modules, depending on size. In theory this means you can install additional synth modules made by other manufacturers conforming to the same Eurocard HP width standard, see BUILDING AND EXPANDING box.

Currently about 18 to 20 different modules are available with another 7 or so in various stages of design and production (see list). For this review we were supplied with two racks bursting full of modules.

The first is a standard RS Integrator 'off the shelf' configuration called System 1 and comprises of:
RS15 case
RS90 VCO (X2)
RS110 Multi-Mode VCF
RS180 VCA (X2)
RS60 ADSR (X2)
RS20 Ring Mod/Multiple
RS40 S&H/Noise/Clock
RS160 Mixer (Lin)
RS160 Mixer (Log)
RS230 CV Buffer, RS170 Multiple

The second rack we were supplied with is a customised unit comprising:
RS10 case
RS30 Pitch-Voltage/Envelope follower
RS70 Pre-amp/Inverter
RS50 Trigger generator/Pulse shaper/Level shifter
RS110 Multi-Mode VCF
RS210 Filter bank

The modules and racks have a slightly unfinished look about them, being plain brushed aluminium with black screen printing, smallish 'soft feel' knobs and 3.5" (mini) jack sockets throughout. To assist with programming the knobs are colour coded: white for audio/signal paths, grey for CV/control, blue for frequency/clocks, red for ADSR, green for wave shape/width, yellow for res/slew/pan and orange for anything else. A set of similarly coloured patch cords is supplied with each system, which is nice. Both the RS10 and RS15 system cases include a built-in power supply with power input socket and mains switch on the rear panel, although this could be an annoyance if the unit were mounted in a rack or transit case. Overall construction is high and everything feels solid and well built and the units would probably take life on the road quite easily. However I'm not sure I like the current vogue for semi-industrial looking aluminium, looks a little cheap to me.

One feature common to both the VCF and VCA modules is the inclusion of two audio inputs, each with a level control knob. This is welcome as it cuts down on the need to feed signals into the mixer module first which just adds to the number of patch cords hanging around (literally). Also, most of the CV modules have a direct 1V/Oct input (for keyboard or sequencer) and a variable CV input with level knob (for modulation). Because of the number of different modules here (15) I won't describe every single feature and anyway some functions are self explanatory, but I will try to cover as much detail as I can on the most relevant modules. Unfortunately an instruction manual wasn't available for the review, so I had to make the odd educated guess or resort to my ageing oscilloscope for some of the specifications.

Currently Analogue Systems only produce one VCO module but it contains most of what you expect to find, plus a few surprises. There are five controls: Frequency, CV input level, Waveform shape CV input (X2) and Range. There are five inputs: 1V/Oct in, Variable CV in, Square wave shape CV in, Swath shape CV in and Sync in. The sawtooth output shape can be adjusted from a rising ramp (clockwise), to a triangular waveform (centre) and finally to a falling ramp (anticlockwise). The sawtooth shape is voltage controllable as is the square wave shape and some nice fattening effects can be achieved by modulating these two independently. The range of the VCO is a respectable 0.3 Hz to 17 kHz (about 20 octaves) and I found it to be stable with no drifting. Next to the Frequency knob is a three way switch for: Wide, Tune or -2 OCT. At the Wide setting the frequency can be swept in one continuous turn (a nice touch), while the Tune position allows the VCO to be fine tuned by approximately a fifth. The -2 OCT is similar to tune but also reduces the pitch by two octaves. In the lower ranges the VCO can be used as an additional LFO. There are control inputs for 1V/oct (for keyboard or sequencer) and variable CV (for modulation). A Sync input is also available for resetting the cycle of the waveform to another VCO signal, to get those great edgy, lead synth sounds.

Unlike most VCFs made in the last 10 or 15 years, which are usually designed around Curtis chips, this filter uses a traditional Moog design, the so called 'ladder' resistor type. And while this may not be a bells and whistles 'state of the art' filter, it is, according to the designers, about as close to a Moog filter you can get without buying a Moog. Controls are kept to a minimum: Frequency, Resonance, and input level controls for audio and CV signals. No fancy gizmos or features, just a bread and butter low pass filter. And what a filter too! The sound is what you might call 'sweet' with musical overtones and yep I must admit, very very Moog sounding. By my measurements the frequency response isn't as wide as some other filters (including the RS110) but who cares when a VCF can sound as sexy as this. Feed it with a couple of VCOs and the world is your oyster, beautiful bass lines, screaming lead lines, growling pulses, resonant saws, you name it this filter can handle it, and more.

This is an extremely versatile filter with four simultaneous outputs, Notch (phase), Band Pass, High Pass and Low Pass. The frequency range covers approximately 20 Hz to 20 kHz and with the resonance control turned fully clockwise the filter self oscillates and turns into a very nice sine wave VCO.

Where you might normally expect to find a voltage controllable resonance, this filter instead has a unique separate resonance output with a corresponding resonance input. This is an 'insert' point in the resonance path which allows you to send the resonance signal to an external modifier such as a filter bank, second VCF, VCA or even a delay line or effects unit. The results can be quite exciting and can change the characteristics of the filter pretty dramatically and sometimes a little unexpectedly. An eye has to be kept on the position of the Resonance knob when using some configurations as it is quite easy to overload the VCF. Once this unusual feature is tried you tend to find yourself thinking of more and more devious routes to send the resonance on. The overall character (or timbre) of the filter falls a little short of the RS100 but that's just a subjective thing and considering how talented it is then this is forgivable.

Like the modules above this is another essential 'building block' module. Apart from audio and CV input level knobs the only other control is INITIAL LEVEL, this control lets you add an offset voltage to the CV inputs, which 'opens' the VCA output and allows you to hear an audio signal even if no other control voltage is present. Interestingly this VCA allows for both Linear and Logarithmic voltage control simultaneously. Rather than getting bogged down explaining the theory of Log/Lin control I will just say that Log inputs sound better with dynamic voltage control signals such as an ADSR envelope generator, while Linear inputs perform better with traditional CV signals such as LFO waveforms and stepped S&H or keyboard voltages. The VCA performs as to be expected, cleanly, transparently, with no artefacts and with unity gain. Also bear in mind that it's quite happy handling control voltages through its two audio inputs, which can allow for some complex mixing and controlling of CV signals from other CV sources.

Which brings us nicely to the envelope generator. This has the usual Attack, Decay, Sustain and Release knobs, plus an output level knob. This is adjustable from normal output (+V), though zero (centre position) to inverted output (-V). Of the two 3-way function switches one gives triggering options for: HOLD/STANDARD/ONE SHOT. The other activates a very useful built-in trigger LFO whose options are: GATED REPEAT/STANDARD/AUTO REPEAT. In Gated or Auto Repeat mode the internal LFO rate is adjusted by the Release knob. If this switch is in Auto position the LFO constantly triggers the ADSR function, while in the Gated position the LFO only triggers the ADSR when an external control signal is present at the gate/trigger inputs. An LED shows the rate of the LFO or the presence of an external gate/trigger. The voltage control option, while welcome, is a bit limited as it only offers simultaneous control over the Decay and Release times. I haven't seen a built-in LFO feature like this since the EDP Wasp. It's a brilliant little featurette and makes it dead easy to set up funky, syncopated triggering effects when using this ADSR with a sequencer or another LFO.

Regular readers of SOS might know of my love of LFOs, you can never have enough of them I say. This one is pretty well specified with a frequency range that extends from sub-sonics into audio (0.02 Hz to 1.4 kHz, in two ranges) and an LED indicates the LFO rate. There are four waveforms, Sine, Triangular, Square and a variable Sawtooth (rising or falling ramp), all are available simultaneously and all except sine have output level controls. The waveforms don't exhibit any uneven swings or lumpiness and it sounded perfectly stable. It's worth noting that although RS80 doesn't use a 1V/Oct CV input it will track a Hz/Volt CV signal, which could be useful if you have an old Korg or Yamaha analogue synth. The Reset input allows you to sync the LFO waveform cycle to keyboard or sequencer trigger control or alternatively lets you to sync it to a VCO. With the right settings it can track a VCO over a wide range making it a perfectly serviceable audio oscillator. It would be nice if a variable delay was included (for fading up the waveform), but it's an effect that can be patched together with a spare ADSR/VCA.

No controls on this module just sockets and a great sounding ring modulator. This RM exhibits little or no signal breakthrough when only one signal is present on either of the X or Y inputs. As is usually the way with ring modulators it's tempting to do all the cliché effects, Daleks, metallic sounds, FM type stuff but this module also tolerates control signals and unlike some ring modulator designs, responds well to slow moving control voltages to produce classic VCS3 'bowing' effects. Which figures, because the design is based on the type used in EMS synths. Another interesting 'scrambled' effect can be achieved by feeding a complex signal (such as a guitar, MIDI synth or even a mix) into both inputs simultaneously.

But I must admit to being mildly disappointed with this module, only one ring modulator section and four interconnected mini-jacks, personally I think they should have put two ring modulators in and left out the extra sockets.

Another useful module, this time containing a white noise generator, a sample & hold circuit and an LFO/clock. The noise generator produces a basic white noise signal, at control level, with a single knob for output level. To get other types of noise (sometimes referred to as pink or red noise) you will need to feed the noise signal into a a VCF or filter. The LFO/clock produces a basic square wave output (with LED and Rate knob) covering a few Hz. The Sample & Hold has an external source input, a One Shot push button and an output level knob and socket. Initially I must admit to a few minutes of head scratching with this module. Usually, (in my experience) a sample & hold circuit would be internally connected to the noise generator and LFO/clock so as to produce a random CV signal as a default setting without any patching. However to produce any meaningful results with this module you need to patch the noise generator output into the S&H external source input and the LFO/clock output into the external clock input. This patch produces a basic, stepped random voltage at a rate set by the LFO/clock, however you can substitute the noise signal with any control voltage and the internal clock signal with any LFO or gate type control.

This module is used primarily for interfacing with the outside world. The Pre-Amp section has a low level input suitable for microphone and guitar levels and a high input for line level signals. Alternatively, line level signals can be fed into the low level input for overdrive effects. The Inverter/Pre-Amp section is unusual because it performs different functions depending on whether the input is audio or control. There are two control knobs Level and Slew. When used with an audio signal the Level knob has a null centre position which a mutes the output. Turn the knob clockwise and you get a normal but boosted audio signal (max gain X10), turn it anti clockwise and you hear an out of phase signal. Adjusting the Slew control acts like a simple low-pass filter and attenuates any high frequencies. However, when putting a control voltage through the Inverter the Level knob allows the signal through unchanged in the null position, boosts it when turned clockwise and boosts and inverts the voltage in the opposite direction. This function is useful for phase reversing LFO waveforms, for panning type effects and inverting sequencer notes, although you can achieve a similar function using the RS230 CV Buffer module which also contains an inverter. When used with control signals the Slew knob slows down (or smoothes out) the changes between stepped voltages, to a maximum of one second and is handy for adding glide or portamento to a keyboard or sequencer CV signal.

This is another module for interfacing with the outside world. The envelope follower works by analysing an input signal and producing an envelope control voltage based on the amplitude of the signal. This works well with most sources but I found that regular audio signals (off tape, guitar, mic, sampler etc.) needed to go through the Pre-Amp module first to get a decent drive signal. A useful Slew knob allows transient signals to be smoothed out but I would like to have seen an LED to show when an input and/or output signal is present.

Don't expect too much from the Pitch to Voltage section, it's basic, functional, monophonic and has input level and Slew knobs. To get any sort of usable results you need to feed it a non-complex, monophonic signal (otherwise the results will be random gibberish) and patch the control output signal into a VCO CV input. Using the P-V to follow a VCO square wave signal it tracked over approximately half an octave before drifting out of tune but fed with a basic 4 note synth bass line it fared better.

This module is where things start getting a little esoteric and Analogue Systems inform me that they have plans for some really weird modules in the future.

The SHAPER can take a signal (audio or control) and produce 10V gate pulses derived from the peaks and transients the signal contains. This works well and is useful for syncing analogue sequencers and envelope generators to bass lines, drum machines or other sequencers. It also features a knob for varying the pulse (gate) width and a voltage controllable pulse width input.

The SHIFTER section is for transposing CV or trigger/gate signals by +/-10V using a variable control where the centre null position allows the CV signal though unaffected. The Shifter also produces a +/-10V control voltage output without any input signal present. This could be useful for manually sweeping or controlling multiple CV sources simultaneously from one knob.

The TRIGGER section is one of the most innocuous looking parts of the whole synth, with just an input socket, output socket and an LED. And yet it's capable of performing all sorts of weird and wonderful functions. Its primary purpose is similar to the Shaper, to output a 10V trigger pulse from an input signal, which it does admirably. However, while the Shaper literally strips out the input and replaces it with a series of on/off trigger pulses, the TRIGGER works by detecting pitch changes in the signal, with altogether different results. The input isn't restricted to audio either, as it can detect changes in CV signals also, such as keyboard and sequencer patterns or joystick movements. But things get a whole lot more interesting when you feed in a complex audio sources and monitor the control output as if it were an audio signal. Used this way the control output 'adopts' (for want of a better word) characteristics of the input signal. The sound is like a cross between a ring modulator and fuzz box, and at lower input levels, like going through a noise gate. But because there are no controls you need to use a pre-amp or a source with a variable output level to get manageable results, the slightest change in level can dramatically alter the sound. I had great fun trying out different sources, tapes, samples, bass lines, drum machines and got some outrageous effects. Taking things a step further some interesting results can be achieved by feeding the control output into other voltage controllable sources and modifiers. According to Analogue Systems the TRIGGER can also operate as a frequency doubler, which you can plainly hear with the right input levels on some audio material. One of their suggestions was that it could be used to transpose a Sync24 drum machine clock signal to 48 ppqn to drive some older drum machines (although I couldn't check this out). Experiment!

RS160 4 : 1 MIXER
There are two types of mixer, Log for audio signals and Lin for control voltages. Although you aren't restricted to how the mixers are used, control voltages can be put through the Log mixer and audio through the Lin mixer. Each mixer has unity gain and a variable master output capable of producing positive or negative signals with a null point in the centre position.

This is a basic, single channel, no frills affair with eight fixed bands at: 75 Hz, 150 Hz, 300 Hz, 500 Hz, 700 Hz, 1.5 kHz, 3 kHz, 7 kHz. The eight knobs simply attenuate, or pass through (without boosting) each band.

Other modules include the RS230 CV Buffer, which is used to distribute a single CV or gate to multiple sources and includes and inverted output and the RS170 Multiple which consists of two rows of 5 interconnected mini-jacks.

I find little to complain about with the RS Integrator. I would like to have seen an input and/or output level LED on some of the modules (as on Roland 100M), to help track down signals and rogue levels. Personally I would have liked to have seen a few more options on the VCO, such as a sine wave output and a soft/hard option for the sync input. A few more octave steps for frequency range would be useful, as would a separate fine tune control. For really complex modulations a third CV input wouldn't go amiss either. Maybe these features could be included on a future, higher spec VCO. Including only one Ring Modulator in the RS20 module is a bit mean. Also, I would have expected to find some form of common buss system to assist in sending keyboard CV, gate and trigger signals to modules such as the VCO, VCF and ADSR, and which cuts down using patch cords unnecessarily. I can't comment on the manual as one wasn't supplied but it's being written by SOS' very own Gordon Reid so there shouldn't be any problems there. Comparisons with the Doepfer range are inevitable and when compared to a Doepfer system using similar modules the RS Integrator works out slightly cheaper, partly due, no doubt, to the fact that Doepfer modules have to be imported from Germany. And I'm sure it must have crossed a lot of peoples minds that RS Integrator and Doepfer 100 system look spookily alike. Well they would because they're based around the same rack case and if this means the beginning of a new 'standard ' then it's probably a good point. Anyway, the Roland System 700 and Moog Series 3 looked almost the same and their modules weren't even interchangeable.

The custom system supplied for reviewed here will set you back about £1450 (incl. VAT). However try buying a equivalent second-hand 22 module, Roland 100M system and you could be looking in the region of £2500 or more. I'm not even going to consider the cost of a similar Moog, Arp or Roland System 700, my hair would turn grey. On the whole this is a superb analogue modular system, well designed, full of comprehensive features, solidly built, expandable and reasonably affordable. Even the basic Mini System should be capable of producing some pretty complex sounds and at £595 is competitively priced, (though no MID-CV interface is included) and makes a good place to start building larger system from. The oscillators are wide ranging and stable and the filters are particularly well specified for this price range. The RS Integrator may not be the best choice for beginners or 'MIDI heads' but if you're an analogue purist or analogue appeals to and you're not too intimidated by all those knobs and sockets then it is definitely worth considering. The only problem could be availability as Analogue Systems are selling them as fast as they can make them, if I were you I'd place my order now.




Price: (see list)
Specification: (see list)
Analogue Systems : Tel/Fax: 01726 67836
Online info and spec can be obtained at System Solutions:

A well designed system, available in standard and custom configurations. The excellent expandability and limitless patching configurations make this a totally open ended system. Beginners may feel a little intimidated by all those controls but this is a superb and 'affordable' modular system for anyone serious about analogue synthesis.


Excellent range of sounds and features.
All analogue, yet stable.
Almost infinite patching possibilities.
Compact, well designed and built.
Easily expanded using standard Euro HP modules.
Affordable modules.

Supply your own MIDI-CV interface or CV keyboard.
Current VCO module could do with more options.
Modules have no input/output level LED's.
There's probably a long waiting list.



Currently there are two RS Integrator 'off the shelf' systems available:

MINI SYSTEM : £595 incl. VAT
RS10 3U rack case
RS110 Multi-Mode VCF
RS20 Ring Mod/Multiple
RS40 S/H/Noise/Clock
Assorted patch leads
Instruction manual


SYSTEM 1 : £949 incl. VAT
RS15 6U rack case
RS90 VCO (X2)
RS110 Multi-Mode VCF, RS180 VCA (X2)
RS60 ADSR (X2)
RS80 VCLFO, RS20 Ring Mod/Multiple
RS40 S&H/Noise/Clock
RS160 (Lin)
RS160 (Log)
RS230 CV Buffer
RS170 Multiple
Assorted patch leads
Instruction manual
Wooden cabinet systems are also available.



This is the full List of RS Integrator modules, current and in production, prices range from £17 for an RS 170 to £215 for the RS15. Call Analogue Systems for up to date prices and availability :

RS10 3U, 84 HP 19" case with internal power supply.
RS15 6U, 2x 84 HP 19" case with internal power supply.
RS20 Ring Mod/Multiple sockets.
RS30 Pitch to Voltage & Envelope Follower.
RS40 Noise, Sample & Hold, & LFO/Clock.
RS50 Trigger Generator, VC Pulse Shaper & DC Level Shifter.
RS60 VC ADSR with auto repeat.
RS70 Pre-Amp, Inverter, Slew.
RS80 VC LFO: Sqr, Saw, Sine, Tri, Sync.
RS90 VCO, Square, Saw, CV variable wave shapes, Sync.
RS100 Low Pass VCF (Moog 'ladder' type).
RS110 Multi-Mode VCF.
RS120 Comb Filter (phaser/flanger).
RS130 Programmable scale generator.
RS140 MIDI to CV converter.
RS150 Sequential Switch Mixer/VCA.
RS160 4 into 1 mixer, 2 types: Log (for audio) or Lin (for CV).
RS170 Dual 5 way multiples (3.5" mini jacks).
RS180 VCA with log and lin CV inputs.
RS190 Advanced Clocking Device.
RS200 3x 12 step analogue sequencer (similar to TH48).
RS210 Eight octave fixed filter bank.
RS220 Joystick.
RS230 CV Buffer/Inverter.
RS240 Envelope Generator (EMS trapezoid type).
RS250 Trunk Line - brings audio to rear panel.
RS260 Voltage Quantiser.
RS270 Adapter/Converter - 3.5mm-5mm, and phono sockets.

Each RS Integrator rack is 3U high and 84 HP wide, the module widths are measured in horizontal pitch or HP. To work out how many modules will fit in a case, add together the widths of each module using the HP measurements (1HP = 5.08mm))

All modules are 12HP wide except:

RS20/150/170/230/250/260: 6HP
RS110/130: 18HP
RS200: 84 HP

VC: Voltage Control.
VCO: Voltage Controlled Oscillator.
VCF: Voltage Controlled Filter.
VCA: Voltage Controlled Amplifier.
ADSR: Attack, Decay, Sustain, Release.
LFO: Low Frequency Oscillator.
Clock: A basic LFO, square wave only.
RM: Ring Modulator.
S&H: Sample and Hold.
Gate: An on/off control signal sent for as long as a key is pressed.
Trigger: A short on/off pulse similar to Gate but only sent at the beginning of a note.
FM: Frequency Modulation.
PWM: Pulse width modulation.
Noise: A rushing sound, also red noise, pink noise and blue noise.
Log: Logarithmic scale.
Lin: Linear scale.
1V/Oct: Chromatic control standard used by Moog, Arp, Roland etc.
Hz/Volt: Chromatic control standard used by Yamaha and Korg.
Slew: A type of portamento, sometimes called an Integrator, acts like a low pass filter on audio signals.
Resonance: Filter resonance, sometimes called Q or Emphasis.
Null Point: Zero output.
Buss: System of internal connection between modules.


Currently RS Integrator and Doepfer Modules are interchangeable as both fit in the same 3U Eurocard case, using the HP measurement system. A Eurocard rack is 84 HP wide, so it's just a question of checking the width of the modules you wish to use and add them together, any spaces can be filled with a blanking panel.

Both manufacturers use a triple rail power supply (+/-12V, 5V), however a custom PSU cable is needed to connect a Doepfer module to an RS Integrator rack and vice versa.

Compatibility is the name of the game for any product to succeed and if more manufacturers continue to adopt the system used by Analogue Systems and Doepfer then it's going to be easier for users to mix 'n' match synth modules from various sources. This feature is going to appeal to a lot of users as will the news that Analogue Systems also sell the internal power supply separately for anyone adventurous enough to build their own systems from scratch. An ideal situation for DIY'ers and anyone on a restricted budget. If you intend building your own additional modules using kits from the likes of PAiA or using projects in books and magazines then a good place to find Eurocard panels, parts and even complete rack cases, is the current Maplin catalogue. Mind you, I wouldn't advise this route unless you have some experience of electromechanical design and construction. Also, if you blow up your brand new IS Integrator synth in the process Analogue Systems won't be interested in fixing it under guarantee.

Keen eyed readers may be wondering where the MIDI to CV module is. Well unfortunately Analogue Systems won't be producing one until latter later half of 98. Instead they recommend one of the Kenton range, but there are plenty of other suitable MIDI/CV units also available. Alternatively you could plum for a second-hand analogue CV keyboard. Either way if you don't have a suitable controller you need to allow for one in your budget.

Instruments like this make extremely useful teaching tools because of the very graphic and obvious way signal paths and connections can be seen and implemented. Modular synthesis is, after all, what many electronic instruments are in basic form, a collection of sources, filters, modulators, modifiers and controllers.

OK, I admit modular synthesis can be a pretty specialised area of music and unless you move in the right circles it's not something you come across too often. It's also not for the faint hearted or total novice as some knowledge of sound theory is required. But persevere and you'll be amply rewarded with some complex, weird and wonderful sounds and textures.

Modular synthesisers were originally developed in the 1950's and 60's and were frequently called wallpaper synths because of the sheer size of the things, often stretching across a wall, hence the name. They came into their own and into popular culture in the 1970's with bands such as Tangerine Dream, Kraftwerk,, Tonto's Expanding Head Band, Tomita, Keith Emerson, Rick Wakeman and of course the ultimate modular evangelist Walter/Wendy Carlos.

A typical modular system consist of banks or blocks of sound generating, modifying and controller modules such as oscillators, filters, amplifiers, envelope generators, modulators, mixers and sequencers. Every module has input and output sockets that are used for interconnecting with each other. They don't have MIDI, memories or pre-sets and they very rarely have hard wired connections internally, everything is connected across the front of the modules using patch cords.

The underlying principle of modular synthesis is Voltage Control. For example, a typical analogue keyboard generates a different voltage for each key (CV), plus a separate on/off voltage for each key, called a gate or trigger. The CV signal can be used to control a Voltage Controlled Oscillator (VCO) to produce a different pitches while the gate control signal is used to trigger an envelope generator (ADSR) to give dynamics to the sound.

So to produce a basic playable sound you would need a keyboard controller, a source such as a VCO, a VCF to add tonal variation to the sound of the VCO and an envelope shaper connected a VCA to vary the dynamics of the sound.

Another fundamental aspect of modular synthesis is that there is little or no difference between audio and modulation signals and practically any input or output can be connected to anything else. The audio output of a VCO can be used to modulate the control input of a second VCO, a VCA can be used to modulate a control voltage and a mixer can mix CV signals just as an audio mixer would.

Copyright © 1998 Chris Carter / SOS Publications.