Modular synthesizer



The modular synthesizer is a type of synthesizer consisting of separate specialized modules connected by wires (patch cords) to create a so-called patch. Every output generates a signal - an electric voltage of variable strength. Combining the signals generated by multiple modules into a common audio output allows a potentially infinite number of configurations, leading to a potentially infinite number of sounds.

There exist many different types and sub-types of modules - even modules with the same basic function will have different inputs, outputs and controls on various models. There are some standards which manufacturers followed for their range of synthesizers, however, connecting synthesizers from different manufacturers often requires converters.

Some standard modules found on almost any modular synth are: Modular synthesizers were largely replaced by highly integrated keyboard synthesizers, racks of MIDI-connected gear, and samplers. However, there continues to be a loyal following of musicians and manufacturers who prefer the physically-patched approach, the flexibility and the sound of traditional modulars.
 * VCO - Voltage-controlled oscillator, which will output a pitched sound (frequency) in a simple waveform (most usually a square wave or a sawtooth wave, but also includes pulse, triangle and sine waves).
 * VCF - Voltage-controlled filter, which attenuates frequencies below (high-pass), above (low-pass) or both below and above (band-pass) a certain frequency.
 * VCA - Voltage-controlled amplifier, which controls the amplitude.
 * Envelope generator - this circuit, on receiving a trigger pulse and/or gate, produces a voltage which changes in a predictable, repeatable manner over time. It can be triggered either manually (for example, by an electronic keyboard) or automatically (for example, by a sequencer). This envelope is most commonly used to control the amplitude of the sound, by routing it to the control input of the VCA or the timbre of the sound, by routing it to the control input of the VCF. This technique can be used to create (synthesize) the volume and timbre contour of naturally decaying sounds such as a piano. The patchable structure of the synthesizer makes it possible to use the envelope generator to modulate other parameters such as the pitch of the VCO, the width of the pulse wave on the VCO and so on.  The most common form of envelope contour is the ADSR, although some electronic instruments, such as those produced by Buchla & Associates or the Wiard Synthesizer Company use the simpler AD or AR contour which can be mixed to form an ADSR (Attack, Decay, Sustain, Release) envelope.
 * LFO - Low-frequency oscillator, the output being a low frequency waveform (this is usually below 20 Hz which becomes a pulsating rhythm rather than an audible tone), usually a sine or triangle wave and used as a control voltage for some other module (for instance, to modulate the frequency of the VCO's output).
 * Ring modulator - Two audio inputs are utilized to create sum and difference frequencies while suppressing the original signals. This gives the sound a "robotic" quality.
 * Mixer, a module that combines multiple signals into one.
 * Sample and hold, which takes a "sample" of the input voltage when a trigger pulse is received and "holds" it until a subsequent trigger pulse is applied.
 * Sequencer, which produces a sequence of notes, usually a music loop.
 * Slew Limiter - smooths off the peaks of voltages. This can be used to create glide or portamento between notes. Can also work as a primitive low-pass filter.

Historic manufacturers of modular synthesizer hardware
The earliest commercial modular synthesizers were developed, in parallel, by R.A. Moog Co., and Buchla in 1963. The synthesizer both broadened the spectrum, and greatly eased the creation of electronic music, which before was made via tape splicing, use of primitive electronic oscillators, and earlier electronic or electromechanical instruments such as the theremin and theOndes Martenot. ARP, Serge, and EMS versions were soon to follow. In 1976, the Japanese company Roland came out with the System 700. Also in the mid-1970s, the mail-order electronics-kit vendor Paia Electronics marketed two different lines of simple DIY modular synthesizer systems.



Modern manufacturers of modular synthesizer hardware (alphabetical)

 * Analogue Solutions (Concussor)
 * Analogue Systems (RS Integrator)
 * Bananalogue
 * Blacet Research
 * Buchla & Associates (200e)
 * Club of the knobs
 * Curetronic
 * Cwejman
 * Cyndustries (Cynthia)
 * Doepfer Musikelektronik (A-100)
 * Elby (Panther Series)
 * Livewire
 * Metalbox
 * Metasonix
 * MFB
 * Modcan
 * Oakley Sound Systems
 * PAiA Electronics
 * Plan B
 * Sound Transform Systems (Serge) (Sound Transform Systems does not currently maintain a web page. Link leads to fan site w/comprehensive information on Serge synthesizer)
 * Synthesis Technology (MOTM)
 * Synthesizers.com
 * Technosaurus
 * Wiard Synthesizer Company

Hardware offerings range from complete systems in cases to kits for hobbyist DIY constructors. Many manufacturers augment their range with products based on recent re-designs of classic modules; often both the original and subsequent reworked designs are available free on the WWW, the original patents having lapsed. Many hobbyist designers also make available bare PCB boards and front panels for sale to other hobbyists.

Modular synthesizer software (alphabetical)

 * Alsa Modular Synthesiser http://alsamodular.sourceforge.net/
 * ARP 2600 by Arturia
 * Bidule By plogue
 * ChucK
 * CreamwareAudio Modular III
 * Csound
 * jMax
 * MaxMSP
 * Moog Modular V by Arturia
 * Pure Data
 * Reaktor
 * RolloSONIC
 * SpiralSynthModular
 * SuperCollider
 * SynthEdit
 * SynFactory
 * SynthMaker
 * Tassman by Applied Acoustics Systems
 * Vaz Modular

Computers have grown so powerful and inexpensive that software programs can realistically model the signals, sounds, and patchability of modulars very well. While potentially lacking the physical presence of desirable analog sound generation, real voltage manipulation, knobs, sliders, cables, and LEDs, software modular synthesizers offer the infinite variations and visual patching at a more affordable price and in a compact form factor.

Semi-modular synthesizers
A modular synthesizer has a case or frame into which arbitrary modules can be plugged; modules are usually connected together using patch cords and a system may include modules from different sources, as long as it fits the form factors of the case and uses the same electrical specifications.

A semi-modular synthesizer on the other hand is a collection of modules from a single manufacturer that makes a cohesive product. Modules may not be swapped out and often a typical configuration has been pre-wired. However, the manufacturer provides mechanisms to allow the user to connect modules in different orders.

Matrix Systems
Matrix systems use pin matrixes or other crosspoint switches rather than patch cords. Historic examples with pin matrixes include the EMS Synthi 100, EMS VCS-3, ETI International 4600, Maplin 5600. The Arp 2500 used a matrix switch.

Patch Override Systems
The different modules of a semi-modular synthesizer are wired together into a typical configuration, but can be re-wired by the user using patch cords. Some examples are the Arp 2600, Anyware Instruments Semtex, the Cwejman S1, Korg MS-10, MS-20, MS-50, PS-3100, PS-3200 and PS-3300.

Electronically Reconfigurable Systems
Reconfigurable systems allow certain signals to routed through modules in different orders. Examples include the Oberheim Matrix and Rhodes Chroma, and Moog Voyager.

Hybrid modular synthesizers
Hybrid synthesizers use hardware and software combination. In alphabetical order:
 * Clavia Nord Modular and Clavia Nord Modular G2 by Clavia, these are however 100% digital modular synthesizers.