Modular Synths - a very quick introduction

As I get lured back into eurocrack land, it's possibly time I finished this off. Can't remember when I started it but several years ago. Presumably it was intended for something but a (very) quick scan shows I probably tossed it off in a few spare moments. I don't know if it's useful or not, see what you think:

• analogue modular synths: a starter's guide

Getting started with a modular can be a daunting thing and if you want to make some noises quickly, hopefully this little, quickly-penned guide will help describe the important connections, the modules, the acronyms. It is neither complete nor exhaustive but could grow as (if) more ideas and tips occur.

So what's a modular synth anyway? A scary panel full of knobs and wires, typically, but it's only when you break them down into individual synthesizer modules with their specific functions and connections that it starts to make sense. Maybe there will be a better answer to this later or maybe it'll dissolve into philosophical pap, who knows?

Anyway, a modular synth is one in which no connections are made between the various synth components, the exception to this being some modulars with MIDI interfaces and pre-wired connections - usually for the VCOs and envelopes.

A semi-modular synth (e.g. Korg MS20) is one where the most common patching is made internally so you can make a noise without cables. There are patch points too, so you can change the signal flow to a greater or lesser extent depending on the synth.

1. The most common terms

2. VCO

Voltage Controlled Oscillator - sometimes you'll hear of a DCO too, which is a Digitally Controlled Oscillator. This is still analogue but with a digital clock controlling tuning and probably not relevant to modulars¹. The voltage control bit just means that voltage is used to set the pitch so you can play it conventionally. Other oscillator terms that come to mind include VCDO (Voltage Controlled Digital Oscillator) as found in the Digisound modular.

The VCO, often called simply the oscillator, is the heart of an analogue synth and typically features a number of waveforms - ideally you'll have sawtooth, square, triangle and, if you're lucky, sine. Of these the square wave may be the only one whose pulse width is variable but on some synths the other waveforms might allow this too. We'll look at what you can do with pulse width a little later. Hopefully all waveforms should be available simultaneously so you can pipe them around your modular freely.

An important point to remember early on is that modulars typically have two types of signal - audio and control voltage. Some modulars even suggest these should be treated separately while in other modulars that idea is frowned upon. Although oscillators, noise generators etc. are audio signals, they should still be candidates for sticking into voltage control inputs, as we'll see.

To start with, if you connect any of these waveforms straight to your mixer or soundcard with no voltage control present, you'll hear a constant tone. The sawtooth is the richest, most full-sounding waveform and very popular in subtractive synthesis (i.e. synthesis where you use a filter to remove harmonics). The square wave is more hollow-sounding and contains only the odd-numbered harmonics. If there's a pulse width control, adjusting this will change the sound, gradually becoming a thin, nasal-like pulse. Tonally the transition is roughly like a morph between a clarinet and oboe. Your VCO should have a voltage input for pulse width and this can be used to simulate the action of moving the knobs using a voltage source such as an LFO or EG.

Drones are all very well but sooner or later you'll want to play the VCO from a keyboard or sequencer. For this a CV (Control Voltage) input is required. A VCO will typically have a couple of voltage inputs at least, and if not a mixer module will come in handy to mix voltages together. Initially you'll connect the CV signal taken either from a MIDI interface or from a CV keyboard - a CV derived from note pitch. Most modulars these days are 1V/Octave meaning that for every volt supplied the oscillator increases in pitch by one octave. If your modular has a voltmeter you can even see this and get a feel for what's going on.

Your VCO will probably have some CV inputs with an adjacent knob for "CV amount". While not usually desirable for conventional keyboard pitch, this is useful for other modulation types - for example if you are modulating pitch by an LFO to obtain vibrato. The mod amount knob or CV amount knob, whatever, is used to bring in the vibrato once the LFO patch connection is made. When you start getting more advanced you might use an envelope and VCA to fade in the modulation automatically...

A VCO might have octave switches, possibly labelled as in organ pipe footages where a 16' pipe is an octave below an 8' pipe. Some have a simpler octave up or down switch and some have none at all, or a large frequency control, hopefully with a fine tune also. An oscillator can also be synchronised to another - check if you have a sync input. If so, connecting the output of a second VCO (a square wave is typically ideal for synchronisation due to the hard edge of its waveform but experiment with others) will cause the synced oscillator to restart in line with the master. Here a diagram would help but for now try it out and then experiment by changing the pitch of the synced oscillator manually. If you like the sound, you'll probably already be thinking about connecting a modulation source to the oscillator's pitch to simulate your knob turning automatically. If so you're getting the idea why modulars are so darn addictive!

1. VCF

The Voltage Controlled Filter is a key component of subtractive synthesis and many different types are available to modular owners. A typical filter works by removing some of the harmonics from your VCO waveforms and also emphasising some of them at the cutoff point. The two main controls to achieve this are cutoff frequency and resonance, the latter also known as Q or emphasis - and probably even wackier things too. Filters are a big subject so we'll look at them in more detail later but for now it's enough to think of some of the most common sorts, which are low pass, high pass and band pass. The names indicate the type of filtering done - the low pass filter gradually filters out all but the lowest harmonics. If you have a filter with these three modes it's sometimes referred to as a multimode filter. Try out each and see what the differences are.

If starting with a pure waveform such as a sinewave you shouldn't hear much difference since a sine contains only the fundamental and no harmonics. However, depending on the filter design and the resonance amount, you may hear something change. This is because analogue filters tend to introduce distortion - often almost imperceptible, but when the input signal level is high the resulting overdrive can be interesting. Sometimes you might even use an attenuator to boost your signal in order to deliberately overdrive inputs. The Minimoog Model D has an external input to the filter and if you routed its own headphone output back into the filter, a classic Moog overdrive was the result. Don't try this on a Voyager unless you're prepared for disappointment though! OK, I digress.

Most filters include voltage control over the cutoff frequency - so are prime candidates for envelope, LFO or keyboard voltage control, to name the obvious three usually included in hardwired synths. Keyboard voltage is just another term for the pitch CV used to drive an oscillator in tune. Some filters allow voltage control over resonance and some even give you the individual outputs of each filter pole. Ah, poles. Let's get to them later, no point getting bogged down in details yet.

1. VCA

Voltage Controlled Amplifier - often used as the final output stage. In common with the filter, the VCA's output is typically shaped by an envelope - so look for a CV input to make the connection. Some VCAs have a gain control that raises their level without needing an envelope - this should be fully down if the envelope is used or there will be a scratching of heads. As with many modules there should be several inputs for signals, several for control voltages and at least one output, possibly a couple of duplicated outputs. There may also be linear or exponential inputs for the control voltages. We'll look at the difference in a bit. 

1. LFO

Low Frequency Oscillator, sometimes also known as a Modulation Generator (MG), by Korg anyway. It is very like a VCO, in fact some are also voltage controlled but the simplest ones don't offer this. It's an oscillator but if you connect to a sound system, the chances are all you'll hear is a series of pops. It's low, see. At its highest frequencies you should hear a tone but this depends on the range of the LFO. The lower and slower it goes, the longer you have to gradually open a filter or sweep oscillator pitch. The faster it goes the more strange, atonal stuff you get as you reach audio-level modulation.

An LFO should have the same waveforms as a VCO, some might even include sample and hold - or this could be available as a separate module (we'll talk about it later as if it was). Connect the various waveforms to your VCO and hear the difference. There's typically a visual aid to the speed in the form of an LED. You want lots of LEDs in your modular, no harm admitting it. If you are lucky enough to have a voltage input, you can use other modulation sources, maybe a second LFO, to vary the LFO speed.

1. ADSR

Attack, Decay, Sustain, Release - the traditional 4-stage envelope used to shape the level, the filter etc. Other envelopes are possible, such as the simpler AR or AD envelopes sometimes seen and even complex multi-stage envelopes can be found or VC-ADSR where voltage is used to modify each envelope stage - lots of fun!

I think the name is pretty self-explanatory and each stage easy to understand without me going on about it. One thing that often confuses people is that an envelope is essentially a slew generator - it takes a certain time to reach its maximum voltage (attack time), then if you keep the gate open takes time to decay to the sustain level. Finally when you release the key, the gate ends and the release phase kicks in, here it takes time to reach zero. As these voltages are held in capacitors, a new gate played during the release phase does not start from zero (a sin committed by lots of software envelopes) but from the current voltage. It would take extra circuitry to discharge the voltage at this point - but almost nobody does this because it sounds shit when you do it. Not that this is, in any way, a hobby horse of mine.

Envelopes are triggered by a Gate signal - this is a voltage that remains on until a key is released. They may also be triggered by a regular pulse, say a square wave from an LFO or the clock signal from a sequencer. The gate signal is the traditional output of a CV keyboard or MIDI/CV convertor. Other terms you might hear are single or multi triggering - this is usually the property of the keyboard itself. Single triggering (e.g. the Minimoog Model D) allows smooth legato playing, envelopes are not retriggered if you play legato. A multi triggering synth (e.g. the ARP Odyssey) retriggers the envelopes for every new note, regardless of the nuances of playing. Both have their values of course and it's only flowery hippy types who always play legato, isn't it?

1. EG

Envelope Generator - another name for ADSR, typically.

Patches, patch cords, patching, Apaches

You'll have heard the term patch to mean a complete synth sound or program and patch cords are just the bits of wire used to connect diffferent modules together. With a modular synth you can make connections that never occurred to anyone else and therefore never appear on a fixed architecture synth. Whether you can remember what you did later is another matter but that's part of the adventure. Digital cameras are handy to "store" your patches made with a modular.

1. Ring Modulator

A module that takes two signals and outputs their sum and difference combined. I think that explanation manages to make the ring mod sound boring - but it isn't. You should experiment with sending two sine waves (it's easier to hear what's happening with sines) at different frequencies and hear the bell-like tones that result. Later you'll send more complex waveforms but for now, the ring mod is not just used for Dalek voices, OK?

What, you really want to create a Dalek voice? You'll need a way to get your voice in and combine it with a sine wave, its speed adjusted until it sounds Daleky. I may flesh out this explanation if necessary.

1. Envelope Follower

It strikes me that mention of external processing brings up the Envelope Follower. This creates an envelope shape from an audio signal, so it's very useful for external stuff. Vocoders use them to control band pass filters, the more of these the more you can understand what's being said. Not sure how I got onto that.

1. CV

Control Voltage - voltage sources include envelopes, LFOs, VCOs, sequencers, keyboards, joysticks, armadillos and aardvarks. Voltage is where it's at and you should be aware of the voltage requirements for each module, each input. If combining different modulars, there could be large differences between the expected voltages, some might trigger an envelope on a change between 0 and +5V, another envelope might sit quietly until it is poked with +10V, for example.

1. PWM

Pulse Width Modulation

You remember twiddling the pulse width control manually? Well, with a voltage input you can get an LFO to do it for you. Or another source. If your VCO has a variable sawtooth wave, this gives an entirely different sound to varying the width of a square wave. Check it out. Faster PWM is commonly used as a source of rich, string-like patches.

1. Portamento/Glide/Slew

These terms are often used interchangeably and the process is similar to basic low pass filtering. Feed in a fast, complex LFO and a slew generator will smooth it off, send in notes from a keyboard and hear the differences between notes blur, you get the idea.

1. Linear/Exponential

these are terms that are often used to describe the shape of an envelope stage but apply more widely too. If an envelope has a linear attack it rises steadily and predictably. An exponential curve sounds and feels more natural and some synths even offer variations on the shape, positive or negative curves and so on. For fast sequencer pieces, an exponential curve on the filter envelope decay is instantly recognisable and if you have a linear decay you sometimes have to combine to two envelopes with two speeds of decay to simulate this. Again, a diagram is in order.

1. Sequencer

An analogue sequencer is a joy to behold, especially for the LED-fixated (i.e. all of us). It consists of at least one row of knobs, each sending a voltage. An input clock is used to step through the sequence and each voltage is sent as the step is reached - simple. Sequencers vary but some allow different directions to be selected for each row, steps to be skipped, input voltages to transpose the sequence and so on. Some sequencers can be clocked at audio speeds, generating an audio waveform - think of this like an LFO running very fast and into the audio range. I can either write a short amount about analogue sequencers or a lot - better I write a short amount I think.

1. CV Mixer

You know what an audio mixer is, a CV mixer might well be the same thing depending on the modular manufacturer. Mixing voltages lets you feed more complex signals into a single input plus you can get voltage controlled mixers too in which a voltage source controls the levels. This in turn opens up the possibilities for automated mixing, panning, morphing between audio sources or voltage sources. Sky, limit, that sort of thing.

1. Noise

Noise - assuming you've watched X-Factor, you know what noise is. It appears in different colours: white, red, brown and so on. White noise contains an even mix of all frequencies while pink noise has more emphasis on lower frequencies. Brown is lower still, blue higher and so on. Noise makes a great modulation source as well as an audio source for whooshes, surf, spacey wind and whatnot. It's an ideal source for a sample and hold module to sample and hold...

Oh, and sampled noise is rarely as good because it's not random and quite often you can hear the loop.

1. Sample and Hold

If you feed noise into a sample and hold module, oh you need to clock it too so the module knows how often to sample, you get a random voltage output. You can feed it different signals too, standard waveforms and mixed waveforms, if total randomness isn't your thing.

1. Multis or Multiples

Some modulars have banana jacks where you can stack connections on top of each other. The rest have multiples, a line of jacks in series that allow you to trigger multiple envelopes from a single source and generally connect more inputs and outputs than you usually could. One issue that is worth noting is multiples are not active or buffered. So if you're using them in applications where precision is important, such as oscillator CV input, you might notice some of that analogue magic, reduced range. It depends on your modular, the number of connections, the impedence and probably other stuff like solar prominences, atmospheric neutrinoes and celebrity tweets.

Joystick

Distortion/Waveshaping

Quantization

BBD modules

Bit Crunching

Spring Reverb

Ribbon Controllers

Fixed Filter Bank

Theremin

Voltage/Gate, Trigger Delays

MIDI

A serial interface invented in 1756 designed so that musicians could mime effectively on stage. Superceded in 1822 by the Laptop.

(and here's my most recent module)

1Because of their greater stability a DCO is often seen as 'less analogue' although it served well enough in synths such as Roland's Juno series or the Waldorf Pulse. Multiple DCOs stacked together don't sound as sweet as multiple VCOs though.

SW11

Sonic Weekend was awesome this time, great people is a given but the location was especially good, the producer (Dean Honer) gave it a fresh and very appealing vibe. For the first time I'm actually curious to hear what we did. Recorded some material in the Yurt but alas due to general vagueness the 4-track cassette was used badly and we lost and overwrote and generally fucked up most of the good stuff we did. Hey ho. I also broke the 'open' button and felt awful.

Can't share too many of our activities online though, had way too much fun for that. But I'd considered possibly jibbing out of next year's, that thought now banished. In fact I may actually prepare something for the first time as the prospect of actually recording something worthwhile reared its head, amazing all concerned. The satnat took me a stupid way though, Wales is bloody mysterious!

Ordered my first euro module. It wasn't meant to be an oscillator because I was determined to get processors. Anyway, it's Elements and far from cheap.

Pre-Sonic-Noodling

My smallest rig yet but still fun. Can be lethal if I don't keep the bass under control though.

Funny how resisting writing stuff online makes you feel more powerful. I keep catching myself about to answer some question or post my thoughts as they've been requested. I'm also resisting as many online petitions as possible. I haven't changed the world with one yet and doubt I ever will. Oh, I admit to signing the petition about 'leaving London control and merging with Scotland' but, hey, nobody's perfect. 

Next I'll spend less time online. Sod Winter, Summer's coming!

More noises
https://soundcloud.com/smokyfrog/a4-perc-96bpm

Minis in the sunshine

Today I uploaded the edits for the last 10 library tracks. Didn't boost in Ultramaximiser as something odd happening with the Wavelab render. They can do it if necessary, kept to a clean, clear mix. Need to find a new project, have some ideas but first reviews to complete. Sonic Weekend is coming!

Here's some photos of my Mini and the mods it has had done.

Yes, I snuck in a shot of Bob the bunny, as you would.

As to the mods, I should say I only had them done because the Mini had mods when I got it. Foolishly I failed to observe this and the mods weren't to a high standard either. I therefore took the decision to make the most of the situation and have the mods replaced by Tony's own, to my specifications.
So Tony replaced the botched LFO implementation with his own board and removed the pitch bend amount knob in favour of a dedicated filter FM control. I wanted oscillator sync too and when it's active the pitch wheel only controls VCO2's pitch. When sync is off pitch wheel is routed only to VCO3. There's a central dead zone but not detent now. It means I can, with one hand. control modulation speed and depth, assuming VCO3 is the mod source.
Another change is that the mod mixer now mixes between VCO3 and the LFO or VCO3 and noise. Those switches are nice.
Speaking of switches, there's one more new assignment, which is PWM source (for VCO1 and VCO2). If I select square wave on either of the first two oscs, the PWM amount knob brings in a rather sweet modulation. Lots of versatility and I think worth doing. Tony found an original Moog knob for the PWM amount and it looks great. He blocked off the jacks but I do have an original Moog pedal somewhere, old size, and may dig it out for Glide on/off. Of course one day there might be the aftertouch keyboard with legato-glide switching, you never know. Similar, might make use of the extra VCA already present as a kind of AM, ring-mod-like effect. We'll see how it goes.

It sounds utterly awesome. Some examples to follow I expect.

Eurovision

If I'd had any, vision that is, I'd have kept my large eurorack system. However I'm being drawn back in. I got out of it for a variety of reasons and getting back is more to keep up with the growing trend (and keep any reviews relevant) than because I love weaving my fingers through rats' nests of wires to reach a tiny knob.

I think it was the Waldorf NW1 that first got me thinking about getting another small euro box. I really should have kept that add-on one that I sold too cheaply and full of some useful modules, including that SY02 (IIRC, the MS20 filter that was so much better than the Filtered Coffee rack version). As I still have the Digisound plus various other CV stuff, I won't need all the bog-standard modules I'd ordinarily start with. I'm more interested in exotic oscillators, effects, heck there were a couple in that Roland collection that piqued my interest, no spoilers in case I get one to review. I liked Paul's Braids oscillator too and some of those weird pattern generators. Oh dear.

Fortunately when Paul grew his system he didn't chuck his old box, which I'm going to grab off him next week, bless the lad. Also have my Minimoog to retrieve as Tony was finishing off my PWM mod today, to add to all the others. I opted for a switch to pick the source between VCO3 and the LFO rather than envelope modulation. Will post some pix here and a rough outline of all the mods, just in case it's of interest. Again, I write this stuff as a brain-dump for me rather than for explicit entertainment value for others, so apologies dear readers if it's dull.

As I'm in a confessional mood... I've been half-contemplating getting another Octatrack. Or did I say that already? I hesitate because I keep hoping for a better product from a less obtuse company but another Messe is here and there's no sign. Perhaps Rusty's OcataEd will make it manageable, but I still suspect I'll be happier with something else for those 'long track' backings for the few festivals I'll play from now until I get totally fed up and jack it in. Yeah, get a laptop you're saying. I know.

A random pic just to break up the dreary text. OK, it's not a cheery pic...

Headshock recording session tomorrow. Finished current review today, nothing else pressing so a weekend of music ahead.

A day being an Old Fart

So I went to Blackpool, never one of my fave places, to a festival of 'experimental music' called Other Worlds. A pleasant train trip and quite sunny so all good. I guess I went without much prior knowledge, knowing only that Saturday was sold out so it boded well for some interest. I took a few Headshock CDs in case it was the right kind of experimental and we might want to play there next year. You gotta admire the optimism.

I had printed a map of the various venues, not apparently of any use on the Friday. By a process of elimination I found the one that was open but it turned out the printed start time was wrong. These things happen, still keeping with the optimism. With an hour to kill I bimbled down to the pier, had a beer, took some pix with my phone. Aimed away from the people and the shabby buildings.

Anyway, I arrived at the venue, got another beer (to get in the mood) and, eventually, it started. The first act was a bunch of earnest beardy youths making dischordant drones. Not totally bad, I thought, if a little aimless and structureless. Process sorted, performance to work on, is how I'd mark it if I was being a glib-arsed critic. Next up was a girl with a flute and a looper. It started pleasantly but then seemed to last forever. I got more beer and, looking around, started to feel a bit out of place. Noticed, belatedly, that the majority were young student types (beards not optional), or perhaps these were other acts for the weekend checking out the competition. Reading the programme and getting the general tone, I started to ponder the possibility of catching the early train.
The plan had been, had the music turned me on, that Pat would drive to pick me up but that seemed increasingly unlikely when, third, a bloke in a red wig carrying a red plastic hand arrived. He pretended the hand was strangling him and pretty soon I wanted to help it. He was armed with an ego, a glass of wine and a backing track. I began eyeing the visible exits. Then trying one. I didn't leave any of our beautiful CDs behind.

Speaking of which, I got a free CD on entry. I played it this morning and it left me hugely relieved I'd wasted only one day. I could be totally wrong but it suggested there'd be more pretentious shite. I suspect journos from the Guardian, Quietus etc. would have loved it all whilst stroking their respective beards. Mind you I think they'd love Headshock too so I'm nothing if not delusional. I predict these acts, some of them anyway, will turn up on the Culture Show being feted and admired. When they do I'll die a little inside, more sour grapes from an old, failed artiste who can't recognise new talent if it drones for an hour under his nose.
I wanted to discover something new, different and local and I maintain I'm not jealous of people with real talent. I know quite a few. Speculating further it may be that it's my old preference: music for the heart over music for the head. I prefer not to write negative stuff yet here I am getting it off my chest so I don't have to say it elsewhere and upset anyone. After all, if asked for an opinion I'd have concentrated on positive things because what do I know? Very, very little, it seems. And less by the day.

Pottered in the studio today, did some nice percussive sequences on the Analog Four. I seem to be doing mostly percussion and pads these days, sequences kinda not making me happy, at least conventional ones. Hope I get the vibe back before the Binar gig or it'll be a strange affair. Stranger.

The Laziness Rant

Yeah, I know, a bit rich coming from me...

It struck me recently (OK, today) that what we old codgers have long interpreted as 'dumbing down' isn't quite so straight forward as it seems. People aren't actually more stupid after all, but I do think they're lazier. Furthermore, I think that social media, forums et al are fuelling the laziness. How often have you seen a really basic question posed on a forum that's really badly phrased, containing only a fraction of information or almost no evidence of attempts at diagnosis? Now I know we don't all share a common language and some people have very little experience, but (and here we descend to sobbing nostalgia) in olden times you very likely had to solve those technical problems yourself. And it took a while so you remembered what you tried along the way. If you were really lucky you could call on an experienced pal who could come round and tell you how a compressor worked or why your MIDI module is ignoring notes from your master keyboard. Imagine those days of prehistory when you had to write a letter to a manufacturer, or ring a tech support guy and talk through your issues?

Now what seems to happen is the moment anyone has any kind of issue, they ask the world for help. Total strangers, many with even less experience, many very happy to advise at length regardless. If the answer fits, the knowledge is applied and the asker moves on to the next hurdle. Nobody learns much because nobody needs to. If you don't remember where you found the answer next time the problem arises, ask again. Of course, lots of misinformation will be spread. So wrongness will fill those server farms alongside the good advice, but hey, it's only data, who cares about its quality?

Aaaaah.

I'm starting to feel better now. That must mean I have, amongst my own wrongness, made my point.

I'm committing the same kind of crime in a way because I could make this text more concise, could explain myself better. I could add more examples, diagrams, humour. It'd probably take me a while though and I have a new delay I want to try out in the studio. If it doesn't work as I expect, I won't be asking any questions online. At least not right away. You see, being old I've gone through a load of head-scratching - it's amazing I still have plenty of hair! But the scratching has helped me pick up a few skills (even if I still don't know how a compressor works). BTW one of the most important rules I ever made up was this: Make up your own rules. Don't feel obliged to stick to them.

With this much hypocrisy I really could have a life in politics.

Yesterday I began the awful task of picking through my last novel and simplifying the plot. I think I'd like to do the same thing for my life, but I realise there's far less scope. After all, if your life involves sitting in a chair and either typing or playing a keyboard, there isn't much left to trim...

Happy Easter y'all. Our rabbit Bob got himself wet deliberately this morning so we'd give him a blow-dry. See, I can even do topical. Here he is blissed-out while Pat lets him have it.