A modular synthesiser is a synthesiser consisting of many separate parts — modules — that you can buy independently, and patch together in any way you'd like.
Each module performs a specific task; only a sufficient set of modules is a complete synthesiser. For example, one module might be a single oscillator, as with Moog's 901, or an intertwined pair of oscillators, as with Buchla's 259, or even half an oscillator, as with Moog's 901A and 901B pairing. Another module might be a filter, or an envelope generator.
When assembling a modular synthesiser, it's up to you to determine how many of each module you require, and how best to lay them out inside the case. Or if you'd rather play it safe, there are usually also some standard configurations available to choose from.
When using a modular synthesiser, you can connect its modules together in any order, with a signal path entirely of your choosing. This is usually achieved with patch cables plugged into patch points. There may or may not be an overridable default signal path, in whole or in part, in the form of trunk lines or a bus. If there is, it can still be overridden using the patch points.
Because a modular synthesiser is configurable both in terms of which modules it consists of, and how they're patched together, it's extremely versatile, and therefore useful for inventive sound design. It's ideal for people who continually think laterally.
The first mass produced and commercially sold synthesisers, designed by Bob Moog on the East Coast and Don Buchla on the West Coast, were both modular. (This likely wasn't a coincidence — probably Don Buchla, and certainly Bob Moog, were influenced by Harald Bode's modular effects unit.)
Most people apparently find modular synthesisers intimidating, but given their historic import I can romanticise them, and I love their flexibility for creative sound design. I also find them easier to understand, because — bussing aside — I can see the entire signal path instead of it being hidden from me.
People always think that these big modular synths are very complicated, when actually they are far less complicated than a DX7 because all you do is look at where the patch lead is going from one module to the other and you know what's happening. The general thing about it also is that it's great for experimenting. By that I don't mean that I sit around and experiment, but very often things go wrong. By accident you put a plug into the wrong hole and something wonderful happens — or not.
— Hans Zimmer, 1986
A familiar module might also have novel uses in a different context. For example, a VCA is necessary to change each note's volume over time (two if you want velocity sensitivity), but remember they can also change the strength of any signal, audio or CV. Similarly, a mixer can mix together any waveforms, so it can also be used to add bias (offset a signal).
Presumably for just such a purpose, Moog's CP35 module provides handy constant positive and negative voltage outputs next to its attenuators. Roland's 132 module even defaults to routing its constant voltages into its mixer.
You might be tempted to go a little overboard, Synthesizer IIIc style, and get nine oscillators. Although I haven't tried this, I've given it some thought. If you're multitracking with plenty of tracks to spare, then recording three oscillators three times is probably only a little slower than recording nine oscillators once, especially once you factor in patching them all up in the first place. Once you factor in tuning them all, it's probably much quicker. As a bonus, you can pan the tracks wide, and given the slight instability of analogue circuits, you get three subtle variations of the entire signal path, making for a richer end result.
- "No Presets Allowed" Ralph Denyer, Sound On Sound, Aug 1986, pp. 50—55
- "Behringer System 55" KSS, Mod Wiggler, Jun 2020
- "Mods Rule... OK?" Sam Hearnton, Electronic Soundmaker & Computer Music, Feb 1985, pp. 44—45
- "Modular Synthesis: Producing String Sounds" Steve Howell, Electronics & Music Maker, Jan 1984, pp. 42—43
- "Modular Synthesis: Brass Sounds" Steve Howell, Electronics & Music Maker, Feb 1984, pp. 57—58
- "Modular Synthesis: Bass Sounds" Steve Howell, Electronics & Music Maker, Mar 1984, pp. 78—79
- "Modular Synthesis: Percussion Sounds" Steve Howell, Electronics & Music Maker, Apr 1984, pp. 66—67
- "Modular Synthesis: Synthetic Percussion Sounds" Steve Howell, Electronics & Music Maker, May 1984, pp. 74—75
- "Modular Synthesis: Woodwind Sounds" Steve Howell, Electronics & Music Maker, Jun 1984, pp. 66—67
- "Modular Synthesis: Vocal Effects" Steve Howell, Electronics & Music Maker, Jul 1984, pp. 66—67
- "Modular Synthesis: Using Sequencers With Modular Systems" Steve Howell, Electronics & Music Maker, Aug 1984, pp. 74—75
- "Modular Synthesis: Using Sequencers With Modular Systems" Steve Howell, Electronics & Music Maker, Sep 1984, pp. 64—65
- "Modular Synthesis: Using Sequencers With Modular Systems" Steve Howell, Electronics & Music Maker, Oct 1984, pp. 74—75
- "Modular Synthesis: Click-tracks Continued" Steve Howell, Electronics & Music Maker, Nov 1984, pp. 64—66
- "Modular Synthesis: More on Using Sequencers" Steve Howell, Electronics & Music Maker, Dec 1984, pp. 66—68