Monday, 1 February 2021

Eurorack and Ruin: Building a Modular Synthesiser

I apologise for the lateness of this post. I originally wrote it in the style of a 1970s New Wave science fiction novel, but following complaints from King Features Syndicate and the Catholic Church I had to rewrite large chunks and eventually there was no point.

But it was awesome! The story culminated with a Marxist revolutionary modelled on Pam Grier forcing Buck Rogers a character that resembled Buck Rogers to sodomise God to death so that He would ejaculate the stars and planets etc.

The ultimate point was that we are the abandoned children of a dead God, which is pretty darn deep if you think about it.

But let's talk about modular synthesisers instead. We can talk about New Wave science fiction another time. Let's talk about modular synthesisers. Specifically eurorack.

What is eurorack? It's a set of physical and electrical standards devised in the late 1990s by Doepfer Musikelektronik GmbH of Germany, based on 1980s computer expansion boards. Before eurorack there was no universal standard for modular synthesisers. US-based systems from Moog, Buchla, Serge and so forth were incompatible with each other.

Eurorack took off because it was compact and relatively simple. Now there are several hundred eurorack manufacturers scattered across the globe. Objectively the eurorack market is tiny, but my guess is that there are far more modular synths in the world today than there were in the 1970s, when politically-aware New Wave sci-fi was all the rage. The New Wave was politically-aware, often juvenile, maddeningly erratic, occasionally brilliant, all too often as cliched as the Golden Age sci-fi it pushed aside.

It's pronounced Doop-fer by the way. The name comes from Dieter Doepfer, after whom the company is named. The OE is pronounced "ooh", which is the noise that God made when Buck Rogers penetrated him. The thing about New Wave sci-fi was that the writers were mostly middle-aged white men who were steeped in the prejudices of white mainstream America, so although the genre was ostensibly progressive their vision of liberal enlightenment involved white heroes taking lots of drugs, using the N-word frequently, and having orgies with sexually liberated women who were background extras in the main character's epic life. Non-white people were noble savages and the idea of women having agency was perhaps too transgressive for the 1970s.

We are trapped in invisible cages. We sing songs of revolution in the language of our oppressors; we don't see the bars. Think of all the psychedelic freak-out records of the progressive rock era that were praised to the skies when they were new, but sound like dated jazzy blues-rock now, because the artists involved - and the critics that supported them - were so immersed in jazz and blues-rock that they didn't realise they were making jazzy blues-rock.

We are trapped. And yet as a child I felt that the nihilism of cyberpunk and the thematic emptiness of 1980s space opera revival and mass-market fantasy was unsatisfying, and for all its faults the New Wave of the 1960s and 1970s had at least tried to innovate, but eurorack. Let's talk about eurorack. Big hit of cocaine and eurorack. Here are some beats made with a eurorack synthesiser while you read about eurorack. I'm not going to talk about New Wave science fiction any more. Not going to talk about it.

Keep away from it. Keep away from sci-fi. Eurorack emerged at a point in time when analogue synthesisers were dead and buried. The analogue polysynths of the early 1980s had been swept aside by sample-based workstations such as the Korg M1 and its heirs, and indeed by samplers; tonnes of musicians in the 1990s ignored synthesisers entirely and bought a sampler instead. For good reason. You could do anything with a sampler. They are incredibly versatile instruments.

Back in the 1990s the analogue scene consisted of clones of the Roland TB-303 bass synthesiser and a few legacy modular systems that were staggeringly expensive and esoteric. The TB-303 clones - the original Novation Bass Station, the Control Synthesis Deep Bass Nine, Doepfer's own MS-404 among others - were analogue to varying degrees, but they were specialised tools intended for one role only. They weren't intended to bring analogue back for the masses.

As far as Roland and Korg and Alesis were concerned analogue was the past. The future of electronic music in the 2000s would involve ISDN and ADAT and sample-based digital workstations and Pro Tools and hard disk recording and a hypothetical replacement for MIDI, and in a way they were perfectly correct, because virtual synthesis became massive in the early 2000s and sample libraries are still with us today.

Virtually all modern television music and a large proportion of film scores are performed with sample libraries of orchestras. Thanks to virtual instruments millions of people have access to a recording studio in their laptop that would have cost a fortune as recently as the late 1990s. But there comes a point when flicking through realistic strings presets gets boring. What if you want bleeps, and bloops? Rhythmic bleeps? And knobs that you can twist with your hands, instead of having to assign functions to a control surface?

An example of good modern music that (probably) wasn't recorded with a modular synthesiser. I include this because I want to stress that I'm not a snob; the only thing that matters is how it sounds.

But analogue was just too cool to die. Hip kids wanted analogue synths because some of their favourite records were made with them, from Oxygene and Computer World to Selected Ambient Works and Felt Mountain and Second Toughest in the Infants etc. Made with them or at least with convincing samples of them. Those kids grew up into middle-aged men with a disposable income, and the cost of manufacturing electronic gadgets with knobs and sliders declined, and people are nowadays willing to spend a lot of money on toys. With the world devastated by a viral plague there's nothing else to spend money on if you have it.

There are also good practical reasons for the analogue resurgence. The abstract nature of simple waveforms is timeless; the simplicity and directness of the classic subtractive synthesis model is refreshing; analogue synthesisers tend to have masses of controls, with instant feedback, and they're all right there in front of you instead of being hidden away behind menus; analogue oscillators don't suffer from aliasing.

And they look awesome. In the 1990s no-one could have imagined that CV/Gate would make a comeback, or that it would be relevant in the year 2021. And yet it did. It outlasted Yamaha's mLAN and the University of California's ZIPI; it is the Morse code of musical instrument interfaces.

My first two modules.

What is CV/Gate? Back in the 1970s analogue synthesisers communicated with each other using a mixture of control voltages and gates. Control voltages carried note information, typically using a standard whereby an increase of one volt represented an increase of one octave. Gates were simple on/off signals that were typically used to activate envelopes. There were also triggers and clock pulses, which were simple click noises, and some manufactures had proprietary interfaces, but let's concentrate on CV/Gate. Let's not talk about New Wave sci-fi any more.

CV/Gate became unwieldy when polyphonic synthesisers took off in the late 1970s - each note required a separate CV/Gate channel - so within a few years the world's musical instrument manufacturers ganged together and devised MIDI, a digital protocol that used a 32kbps serial network travelling down stubbly little cables to transmit note information.

MIDI does the job well enough and it's cheap to implement so it still exists today. It supports sixteen channels of polyphonic note data plus clock plus song pointers, albeit that because it's a serial protocol there are microscopic timing issues, which are further exacerbated by USB-MIDI interfaces.

In contrast CV/Gate transmits data at the speed of light, and furthermore because the signals are simple voltages and the connectors are all the same there's nothing to stop you from plugging a CV output into the control input of a filter, for example, or an envelope generator, or an LFO etc. It's a flexible system that encourages experimentation.

At top a work-in-progress, at bottom the final result (so far).

Modular synthesis has a reputation for appealing to tinkerers, and there's a wealth-signalling aspect as well because it's not cheap. The leading practitioners are drawn from the same pool of thin white men and women that make up the roster of Mille Plateaux records; people who wear their lack of incentive to achieve as a badge of honour. None of them like to talk about where their parents' money came from because their parents are hedge fund managers or lawyers or the chief finance officer of Siemens etc.

Eurorack is a bit of a mongrel dog in that respect because it's relatively simple and affordable. Owners of Serge, Buchla, and Moog systems look down at eurorack. "How cute", they say. There's a class system within the world of eurorack, just as there is a class system in the world of backdated Porsche 911s and vintage guitars and everything. If your eurorack is stuffed with modules from Intellijel of Canada or Cwejman of Sweden you will be respected; if you have modules from Behringer or a no-name brand from eBay you're no fun.

I've always associated Buchla synthesisers with the kind of wealthy Californian who owns a house next to a public beach, and has built a wall to block the public from using the beach, and has spent the last decade appealing against legal demands from the local council to have the wall taken down. This person never visits the beach, he just wants to block other people from using it. On the surface they are lovey-dovey supporters of the arts community, but scratch the skin and they are vipers.

I'm digressing here. What if I am the ranting maniac? No, let's move on. I'm not going to pretend to explain the basics of synthesis or talk about New Wave sci-fi any more. My suggestion is that you get hold of Arturia's ARP 2600V, which models the patchable-but-not-quite modular ARP 2600, and tinker with that for a while. For a shade under £600 Behringer makes a recreation of the ARP 2600 that is extensively patchable. For a similar sum Moog makes the Mother-32, which is simpler but has a lovely Moog filter.

The power connectors are keyed, but it's a good idea to make sure that the +12 and -12 pins line up with the appropriate sockets on the module. Doepfer power buses carry CV and gate signals, but only a handful of modules - all made by Doepfer - can use those signals.

Oh, I'll have a go. Modular synthesis is a bit like Lego or assembly language, in the sense that the individual building blocks are simple but the arrangement of blocks can become complex. A modular synthesiser typically has:

- One or more sound sources. Analogue synthesisers of the 1960s and 1970s used VOLTAGE CONTROLLED OSCILLATORS (VCOs), which generated simple waveforms such as sawtooth, square, and sine waves. In the 1980s digital synthesis with frequency modulation displaced analogue oscillators, and in the 1980s and 1990s digital sample players displaced FM, although while this was happening modular was dead as a doornail, so the digital revolution largely bypassed the modular world. Modular synthesis is extremely flexible, and there is no reason why a modular synthesiser cannot dispense with oscillators entirely and use a shortwave radio as a sound source, or a microphone, or the amplified sound of stones.

- The VCO feels into a VOLTAGE CONTROLLED FILTER (VCF), which adds sonic colour to the sound by muffling it (if it's a low-pass filter) or brightening it (if it's a high-pass filter) or making it sound like a 1940s radio (if it's a band-pass filter) or making it sound like a throat (if it's a formant filter) etc.

- The VCF feeds into a VOLTAGE CONTROLLED AMPLIFIER (VCA), that shapes the volume of the sound. Why VCO-VCF-VCA, and not for example VCO-VCA-VCF? Because some filters can make sounds of their own, and if there isn't a VCA at the end of the chain the VCF would never shut up.

- This arrangement by itself would produce electric-organ-style BOOOOOOO noises. One of the things that separates a synthesiser from other electronic musical instruments is modulation; in the classic synthesiser model the the VCF and VCO are controlled by a mixture of one-shot ENVELOPES and repeating LOW FREQUENCY OSCILLATORS (LFOs) that make the sound go whooo or ping or bouncy-bouncy or wubble or bah weep gragna weep ni ni bong or zang-zang-tuuumb with three "u"s.

Shown here with a pair of Arturia Beatsteps. The Beatstep has a combination of MIDI and separate CV and gate outputs, and in this image I'm using the gate from the top Beatstep to control the filter, and the lower Beatstep to control the pitch.

There are also slew generators and frequency dividers and phase locked loops, but they are deeper magic for another time. The simple building blocks above can be combined to produce complex sounds. For example you could feed a short envelope into a VCA that's set up to modulate a VCO, thus producing a little pitch jump at the beginning of each note (as in Vangelis' "Chung Kuo" or the classic shakuhachi-type sound), or you could use an LFO to drive another LFO, thus producing a complex polyrhythmic modulation. That's what I'm doing in this video, I'm modulating an LFO with another LFO:

One element that tends to trip people up - it tripped me up - is gates. With a MIDI synthesiser the keyboard automatically routes NOTE ON and NOTE OFF messages to the envelopes every time you press a key, but with a modular synthesiser you have to manually wire the envelope gates up to the sequencer, perhaps using a MULTIPLE to transmit a single gate to several envelopes.

Modular synthesisers are appealing for their versatility. If you want a Minimoog-writ-large that has six oscillators instead of three you just need to find sufficient space to fit the oscillators, plus a mixer to combine them; alternatively if you want to emulate the classic ratcheting "Berlin school" sequencer sound you can fill your case with clock dividers and trigger-gate converters.

Have you ever read about the EMS VCS3? It's a compact not-quite-modular synthesiser from the late 1960s that fetches five-figure sums on the used market, but with a set of eurorack modules you can duplicate most of its functionality for a fraction of that price. Doepfer even makes an affordable spring reverb. By swapping in different filters it's possible to mimic the classic semi-modulars of the past for less money than an actual vintage unit.

The need to wire up new patches puts some people off, but just because every module has a bunch of modulation options you don't have to use them. I recorded the following little ditty just to see if I could make a plain vanilla patch with Plaits. The tune is essentially a duet between Plaits and a Korg ARP Odyssey, with the Model D on bass:

Let's talk about my modular synth and perhaps some of it might sink in. It's built into a Doepfer LC6 case, which has a pair of 84HP racks. HP stands for horizontal pitch; 84hp is a popular width because it can easily be adapted to fit into a standard 19" studio rackmount. Doepfer makes one-storey, three-storey, multi-storey cases in a variety of widths, and there are alternatives from other manufacturers; the case is essentially just a wooden box with a power supply and some rails.

Another popular form factor is the boat, or skiff:

Technically this is the case for my Behringer Model D. Nonetheless it's a standard eurorack size and could be used to house 70hp's worth of eurorack modules, although unless they were all passive I would need to buy a power supply because the Model D's PSU isn't eurorack compatible.

The LC6 comes as standard with a 75w power supply. The power draw of my system is 13.8w, so my hunch is that I would have to try very hard indeed to overwhelm the PSU. The LC6 case is unpainted and unfinished, so I gave mine a coat of Wickes 310 Magnolia.

Let's have a look at the top row:

Stand by to launch remote control attack ship

On the left is an Doepfer A-118 noise generator, which produces hissy noise and random voltages. It's useful for randomly modulating things or producing percussive noises. I have the impression that a lot of people buy a noise module because they feel that their system needs one, and then never use it. I rarely use mine.

To the right is a Behringer 140, which has a pair of envelopes and an LFO. It's good value at around a hundred pounds. It's designed to mimic the look of the 1970s Roland System 100M. In this image envelope 2 is modulating the A-101 filter and envelope 1 is modulating a VCA that's off the edge of the image. They're both drawing gate inputs from a passive multiplier, although I've unplugged the multiplier's gate source because the holes reminded me of New Wave science fiction.

To the right again is a Doepfer A-101-2 low pass gate. Doepfer makes a range of filters, and I wanted to pick one that was slightly unusual. The A-101-2 is a multifunctional VCF, VCA, and low pass gate -  essentially a VCA that reduces the cutoff frequency at lower amplitudes. Low pass gates are a cheap way of adding colour to a sound, and furthermore some designs don't require power. This particular model has a relatively soft sound, not as thunky as a Moog filter.

To the right of that is a multiplier. Anything plugged into the top socket is routed to the five sockets beneath it. Multipliers are useful for sending the same control voltage to multiple oscillators, or for duplicating gate signals. They generally don't require power.

Moving along is a simple VCA, which doesn't have anything plugged into it. I could in theory send an audio signal to the IN socket, and the output of one of the Behringer 140's envelopes to the CV socket, and the output from the OUT socket would have the original sound with the volume modulated by the 140's envelope.

To the right of that is Mutable Instruments' Plaits, which is a grab-bag of digital synthesis models. It appealed to me because I already have an analogue synthesiser, so there must be other songs to sing. Plaits' range of models includes a virtual sawtooth/square, simple FM and wavetable synthesis, plus a granular supersaw and some drums. At first I was disappointed with it, but after plugging in a bunch of modulation sources (pictured) it came alive. Plaits also has a built-in envelope and low pass gate, so you can use it entirely by itself if you just plug a CV source into the CV input and a gate source into the trigger input.

To the right is a wooden blanking plate, and to the right of that is a TAKAAB 3LFO, which is made by Siam Modular of Thailand. The module's LFOs aren't synchronised with anything, so they're relatively limited - they just run of their own accord - but the unit costs around £46, which is good value for three LFOs. The LFOs run at different rates, with the top fastest and the bottom slowest.

To the right again is a Doepfer A-130 VCA, which is boring but has a separate gain control, so it doesn't require a control voltage to pass a signal. Eurorack is unusual in that Doepfer's first-party modules are generally no more expensive than their third-party equivalents, which is why my system has such a diversity of modules. In terms of online cachet Doepfer has a reputation for being functional but boring.

Just peeking into the frame on the right is a Doepfer A-166 dual logic module. Imagine two sequences of ones and zeroes that run at the same rate. If the two sequences have a 1 at the same time an AND gate will output 1 (1 AND 1 is 1), and an OR gate will also output 1 (1 OR 1 is 1), but an EXCLUSIVE OR (XOR) gate will output 0 (1 BUT NOT 1 is 0).

Did that make sense? I worked it out by plugging things into it and noting the end result. If you plug a bunch of gates or triggers that run at different rates and at different times into the inputs, the outputs will be a selected mixture of all the inputs. The end result is an unpredictable but repeatable sequence of gates that can be mixed with a regular gate to produce interesting rhythmic results.

In this video I've moved the logic module to the top-left of my rack. I'm feeding two gates and a high-speed trigger into the logic module, which doesn't quite work because the trigger isn't active long enough to have much impact on the logic. Nonetheless you can hear how the bassline has a distinctive trilling sound, as if a woodpecker was drilling into the keys.

I modified my system during the course of this blog post. At the extreme top-right I now have a Mutable Instruments Yarns, which is a MIDI-CV converter. It can be set to convert four channels of MIDI input into four separate CV/Gate combinations, or alternatively one channel of MIDI into CV/Gate, Velocity, Modulation, and aftertouch (or two channels of MIDI with CV/Gate and velocity). It also has a step sequencer and a surprisingly complex arpeggiator that can be applied to each channel separately.

In this video I'm using the arpeggiator to convert a slow set of notes into a rhythmic sequence. I'm triggering the drums with a set of audio pulses, which is why they go all over the place. Look at the blinking lights go! That's what modular synthesis is all about. Wires and blinking lights.

Let's look at the bottom row:

The vast bulk of the bottom row is taken up with a Behringer Model D, which is a clone of the Moog Minimoog. It's a three-oscillator monosynth with a wicked filter. It comes in a wooden case:

But as you can see it can easily be removed and added to a eurorack system, in which case it uses the rack's power supply. It has a range of patchable inputs and outputs, but it's not truly modular. There's no way to address the individual oscillators and it doesn't transmit CV, which is unfortunate because it would have been a useful MIDI-CV converter if it did. My rack feels a little bit like a pair of independent synthesisers that happen to share a case.

To the right of the Model D is a simple passive attenuator, which reduces the strength of signals. This is useful if your LFO is too strong. To the right of that is a three-channel mixer, which in the above image is taking both of the outputs from Plaits. Some mixers can be controlled with voltages; this mixer has knobs, only knobs, human-controlled knobs, for a human.

But Have You Considered the Cost?
My suggestion is that you budget a thousand pounds. Aim to spend seven hundred pounds, but accept that you'll actually spend a thousand pounds. Doepfer makes a prebuilt system called the A-100 for £1,800, but it strikes me as an esoteric choice for a beginner because a lot of the modules are very specialised and yet it only has two proper VCOs.

I chose a two-storey case because I wanted to eurorack my Behringer Model D and have a row free for extra modules, but you might want to start with a one-storey case instead. Let's imagine you want a simple analogue synthesiser with some modulation options. You're willing to leave complex sequencing modulation with mathematical operations until you've learned a bit about modular first.

I'll pick prices from London Modular mainly, but there are other shops on the internet (Amazon sells Behringer modules; Thomann in Germany is popular on the continent but bear in mind the prices don't include VAT).

You might choose:

- A Doepfer LC3 84hp one-storey case for £185
- A Doepfer A-111-6 Miniature Synthesiser Voice (10HP, £150)
- An ALM MMMidi MIDI interface (6hp, £90)
- A Behringer 140 dual envelope / single LFO (16hp, £95)

The A-111-6 is a little mini synthesiser with a VCO, VCA, and VCF. It's usable by itself, but without proper envelopes and an LFO the end result is very simple. This setup by itself costs £520 and will at least make noises - it's not a million miles from a Roland SH-101 - but it would be very basic. An Arturia Microbrute is half the price and more flexible, albeit at this point you still have 52 units of space left.

Alternatively you could drop the Doepfer A-111-6 - it feels like cheating - and replace it with a Behringer 112 Dual VCO (16hp, £95) and a Doepfer A-121-3 VCF (4hp, £95) which would come to £560. Alternatively you could do what I did and use Mutable Instruments' Plaits (12hp, £195) as your sound source. One downside of this is that everyone has Plaits, because it's ace, so although people on the internet might not mock you they will not respect you either.

You might want to expand your basic system with:

- A Meng QI Split Multiple/Attenuator (4hp, £55)
- An ALM MCO Digital Oscillator (6hp, £135) for some sonic variation; it would plug into the A-111-6's external input in lieu of a mixer
- A Doepfer A-124 Wasp Filter (8hp, £77)
- A TAKAAB 3LFO from eBay (4hp, £46)

This costs an extra £313 and leaves you with 30hp. At this point however you have two fundamentally different oscillators, two filters, four LFOs (one triggerable, three not), two ADSR envelopes, a MIDI interface and a multiple to split the gates. Alternatively ditch the filter and oscillator and buy a MakeNoise Maths (10hp, £275), and perhaps replace the MIDI interface in the first block of modules with a second-hand Mutable Instruments Yarns, which gives you four channels of CVs and Gates to feed into Maths.

The issue of space is a thorny one; if you start with a one-storey case every extra storey you add will cost £185, when you could have spent an extra £100 and bought a two-storey case to start with. On the other hand if you get bored with a one-storey case and decide that modular synthesis is a waste of time you've saved yourself that extra £100.

Of course you have to ask yourself if you really need a modular synth. They're great fun to play with, but they cost a lot of money and even in eurorack form they're awkward to transport and gig with. The professional musicians who used modular synthesisers in the early 1970s - Keith Emerson, Tangerine Dream and the like - generally abandoned them as the decade moved on, because smaller, more portable keyboard synthesisers and semi-modulars replace most of their functionality.

Many of the classic albums I grew up with - Chill Out, Endtroducing....., Lifeforms, Logical Progression, U F Orb - didn't even use synthesisers at all, they were based entirely around sequenced samples. And for the same money as the setup above a Behringer 2600 and an Arturia Minibrute could duplicate a lot of its functionality. With the suggested builds above I didn't consider the cost of patch cables and I have assumed you already have an audio interface and a computer.

On a personal level I was inspired to build a eurorack system by the existence of the Moog Subharmonicon, which combines an oscillator with a four-step sequencer; it's an appealing thing, but at £800 it's far too expensive for what it is. For the same money I could build a more complex synthesiser, so I did.

Such is the pace of change in the modern age that I bought a spring reverb even before it appears in the main body of the article. Isn't that reminiscent of the non-linear narrative of Kurt Vonnegut's classic New Wave sci-fi novel Slaughterhouse-Five?

More than anything however I was inspired by the fact that Doepfer makes a spring reverb. The A-199. It's only £80 on the used market. I don't have it yet, but one day I will. Both All of the classic semi-modulars of the 1970s had a spring reverb. A spring reverb is a bunch of springs in a metal box with a microphone that sounds like the 1950s. I can't think of a better reason to build a modular system. The chance to own a spring reverb, and for it to mean something and actually have a use.