The Modular Synth

( Picture of one of Hans Zimmer's Modular synths courtesy Synthfool )

A long time ago, in a galaxy far away, before your local music shop was packed with the latest digital synths, even before the early analogue monosynths, if you wanted a synthesizer you had to make it yourself. Modular synthesis is not in itself a different type of synthesis, but refers to the fact that a synth would be built up from individual components (modules) , which would be linked together (patched) in a configuration decided by the person doing the building. 

Compared with today's 'plug and play' synths which come with 100's of presets, GM soundsets, etc, this has the obvious disadvantage that 'recalling' a preset can only be done if your synth is patched together in exactly the same way every time and every controller has to be manually set to the same parameter.

However, the big advantage of Modular synthesis, of course, is that, providing you have the right components, you can build practically anything you want, without being constrained by the 'hardwired' configurations of modern factory built synthesizers. 

The Pulsar/Scope Modular synth, like any other Modular 'soft synth' brings together the advantages of both Modular synths and modern factory built synths. Modular configurations can be saved as patches for total recall later on, and each patch can contain any number of presets, again for later recall. Furthermore, with a software modular, you can re-use each component as many times as you wish within one patch, you never run out of cables, you don't have to dedicate a whole room to the synth and the modules never suffer from physical damage. What's more, each parameter can be controlled by MIDI so parameter changes can be recorded into your sequencer in real-time.

The different versions of the Pulsar/Scope Modular

There are three different versions of the Pulsar/Scope Modular Synth:

Version 1 came with version 1 of the software that comes with the original Pulsar cards. This version is no longer officiall supported, as it has been superseded by later versions. However, this version still works perfectly well and can be downloaded for free from the downloads page. There are numerous excellent patches available for the v1 modular, many of which can be downloaded from the v1 patches page.

Version 2 comes free with all versions of the Scope cards, except ScopeFX. This version is a major overhaul of the Pulsar modular synth. The modules themselves have been redesigned and take up much less room on the screen, and the interface has had many improvements made to it. Read more on the Mod II page.

Version 3, rather than a complete overhaul, can be seen as an upgrade to Modular 2. The new version contained 76 new modules, and also there were numerous improvements to the 'shell' in which modular patches are put together. Unlike versions 1 & 2, modules from versions 2 and 3 are compatible with each other, and so the total number of modules grows considerably with this version.

Although there are various new modules available in the Version 2 software (especially the sequencer and drum synth modules) the other significant differences between the two are all in the interface, so an introduction to the modules in version 1 should still be relevant to users of version 2.

If you are not an owner of the modular, but are interested in reading about it, a good source of information are the v2 and v3 Manuals. All Sonic-Core manuals can be downloaded here, with the Modular Manuals available here (also available in French and German if you navigate to the relevant directory.

The difference components of a modular system:

Oscillators

An Oscillator is almost always the primary sound source for any Modular synth patch, and in very crude terms can be thought of as a generator of sound of some sort, normally triggered by a Midi event. The output of an Oscillator can be something very simple like a pure Sine wave (Sine Oscillator) or it can be complex such as the output from the Waldorf Wavetable Oscillators or from the Wave Oscillator, which you can load with your own samples.

Here's a picture of an Oscillator module from the ARP 2500. Notice how similar its controls are to the Pulsar Multi Osc M2 Module.

The simplest Modular synth patch (at least one that generates, rather than just processes, sound) would have to contain at least one Oscillator as its sound source. along with one of the Amp modules. Such a patch would look something like this (in version 1):

And the signal path would look like this:

Obviously, this patch is not very interesting, and in the sections below you will find sections on the modules which can be used to modify the output of these Oscillators to make it more musically useful.

A full list of version 1 Oscillators can be found here, with further notes, pictures, etc.

A full list of version 2 Oscillators can be found here.

Amps & Envelopes

Once you've got a basic signal coming from your oscillator, you will need to amplify the signal in some way in order to make it audible.  In analogue modular synths, Amps are used to convert a voltage into audible sound. I don't know whether this is strictly necessary in a virtual modular synth (is the output of an Oscillator a voltage?) but the same principles hold true here. We want some way of controlling the loudness of a sound.

Most likely you will also want to use an envelope in order to control the way in which the loudness of the signal changes over time. This will have an enormous effect on the quality of the sound, and is one of the most important factors in determining the eventual output of the synth. 

If you compare the sound of different instruments (or of any sound in fact) one of the many distinguishing factors is the way in which the volume of the sound changes over time.  For example, think of the difference between a church organ which reaches its maximum volume almost instantaneously, compared to, say a violin, where there will be a slight delay before the note reaches full volume.  Similarly, when you take your fingers off a church organs keys, the note will also stop instantly (ignoring the natural acoustics of the church) whereas if a violinist stops playing, the note will ring on for a short while due to the resonance of the violin's body, providing the strings aren't damped by bow or fingers.

Even a single instrument will have different characteristics according to how it is played and this can often be emulated in part using an envelope. Think of a Hi Hat. The initial sound of an open Hi Hat played at the same volume will be the same, but if the Hi Hat is closed or struck again, the latter sound will be very different. Similarly, the sustain pedal on a piano will make the piano play on much longer. If you imagine drawing a graph which shows the volume of the sound over time, this would give you the basic envelope shape needed to recreate that feature.

Some envelopes of the Pulsar modular envelopes also allow you to modulate the shape of the Envelopes according to (eg) Note value or velocity, so that you can have the envelope's character changing as you go up the keyboard or play notes louder. The Modular II envelopes offer even more possibilities in terms of modulation

It's important to mention that Envelopes do not only have to be used to control the velocity of a note over time. They can also be used to control many other modules whose parameters you want to change over time. For example, you might want to use an envelope to control a filter, so that the filter opens up over time as you hold a note. Other uses might be controlling the pitch or pan values of a note over time. You'll find an example of this type of usage on the v1 Envelopes page.

Here's a picture of a 'real' Envelope Generator, next to some Pulsar ones.

Versions 1 & 2 of the modular synth implement the combination of Amp & Envelope in different ways, but the principles are the same. Version one has Amplifiers & Envelopes combined in single units, whereas version 2 splits these components into separate modules.

I've added with a page on the Version 1 amps/envelopes here, as most people will have at least version 1 of the synth. I'll add a page later about the version 2 amplifiers and envelopes.

LFO's

What is an LFO? LFO stands for Low Frequency Oscillator. Like the Oscillators described in the Oscillators section above, a low frequency oscillator outputs an oscillating frequency of some sort, but the output of an LFO is generally much slower (lower frequency) than that of a standard Oscillator. When you hear the output of a Sine wave from a normal sine oscillator, the frequency of the wave is generally so fast that you can't distinguish the individual cycles of the wave, you just hear a continuous tone. With an LFO, the cycle of the wave is so slow that you can (at low frequencies anyway) actually distinguish the individual cycles of the wave. 

LFO's are generally used to modify some property of another module (the pitch of an Oscillator, the amplitude or panning of a signal, etc) in order to create variation in the sound. Obvious examples are creating a tremolo, vibrato, or auto-pan effect, but there are many more uses.

Here's a picture of a 'real' ARP LFO module, next to some Pulsar ones.

Here's a page with details of the version 1 LFO's. Version 2 to follow later.

Filters

The effect of filters on synthesized sound cannot be underestimated - in fact some people feel that filters are the most characteristic feature of a synthesizer, and play the most important role in defining the unmistakable sound of many 'classic' synths.

So what does a filter do? As it's name suggests, a filter removes certain parts of a signal, just as a sieve will remove certain parts of a fluid (for example) which is passed through it. Just as you can control what gets filtered out of a liquid by choosing sieves with different sized and shaped holes, so too your choice of filter, and the settings used, will determine what part of the original signal will be allowed through. 

What is very important to realise, however, is that filtering does not just have a 'reductive' effect, that is to say that filtering does not just result in a weaker, lessened sound. Filtering has a much more dramatic effect on your sound than that because, due to the way it changes the phase relationships of the harmonics within the sound, it can not only attenuate (reduce) some harmonic overtones but it can also boost others, and the resulting sound can differ greatly from the original.

If we go back to our sieve analogy, imagine sieving a mix of wholemeal flour, stones and sugar, with a fine meshed sieve. The 'product' of the sieve will not just be a 'slimmed down' version of what we put into it - it will differ from the original in consistency, colour, density and so on.

For more in depth discussions on the the theory behind filters, I can recommend  parts 4,5 & 6 of the Synth Secrets articles by Gordon Reid  in Sound on Sound.

Here's a picture of a 'real' multimode filter, next to two Pulsar ones.

Here's a page describing the various filters available in version 1 of the Modular, with further explanations of the terminology used to describe the characteristics of the different filter types and controls.

Here's a page listing and describing the version 2 Filters.

Mix And Level

It may be necessary to cut or boost the level of certain signals in the signal chain of your patch, and also to mix the signals from different sources (if you have more than one audible Oscillator in your patch. One common use  is to boost the output of a resonant filter module as these reduce the gain of the signal in order to avoid overloading at high resonance levels.

Read about the version 1 Mix and Level modules here.

Effects

The Pulsar Modular comes with a number of effects with which you can further  modify your sound. Along with the standard flanger, chorus and delay types, there are some more esoteric effects such as Bit Quantizer and  Decimator.

Read about the version1 effects here.

Coming Soon.

Midi, modifiers, etc, etc !