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Modular synthesizer

Modular synthesizer

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The modular synthesizer is a type of synthesizer
A synthesizer is an electronic instrument capable of producing sounds by generating electrical signals of different frequencies. These electrical signals are played through a loudspeaker or set of headphones...

 consisting of separate specialized modules connected by wires (patch cords) to create a so-called patch. Every output generates a signal – an electric voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...

 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:
  • VCO – Voltage Controlled Oscillator
    Voltage-controlled oscillator
    A voltage-controlled oscillator or VCO is an electronic oscillator designed to be controlled in oscillation frequency by a voltage input. The frequency of oscillation is varied by the applied DC voltage, while modulating signals may also be fed into the VCO to cause frequency modulation or phase...

    , which will output a pitched sound (frequency) in a simple waveform
    Waveform means the shape and form of a signal such as a wave moving in a physical medium or an abstract representation.In many cases the medium in which the wave is being propagated does not permit a direct visual image of the form. In these cases, the term 'waveform' refers to the shape of a graph...

     (most usually a square wave or a sawtooth wave, but also includes pulse, triangle and sine waves).
  • Noise source - A generator that supplies "hiss" sound similar to static, which can be used for explosions, cymbals, or randomly generated control signals. Common types of noise offered by modular synthesizers include white
    White noise
    White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency...

    , pink
    Pink noise
    Pink noise or 1/ƒ noise is a signal or process with a frequency spectrum such that the power spectral density is inversely proportional to the frequency. In pink noise, each octave carries an equal amount of noise power...

    , and low frequency
    Low frequency
    Low frequency or low freq or LF refers to radio frequencies in the range of 30 kHz–300 kHz. In Europe, and parts of Northern Africa and of Asia, part of the LF spectrum is used for AM broadcasting as the longwave band. In the western hemisphere, its main use is for aircraft beacon,...

  • VCF - Voltage Controlled Filter
    Voltage-controlled filter
    A voltage-controlled filter is a filter whose operating characteristics can be controlled by means of a control voltage applied to one or more inputs...

    , which attenuates frequencies below (high-pass), above (low-pass) or both below and above (band-pass) a certain frequency
    Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...

    . VCFs can also be configured to provide band-exclusion, whereby the high and low frequencies remain while the middle frequencies are removed.
  • VCA - Voltage Controlled Amplifier, which varies the amplitude
    Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...

     of a signal in response to a supplied control voltage.
  • EG - triggering an Envelope Generator produces a single, repeatable shaped voltage pulse. Often configured as ADSR (Attack, Decay, Sustain, Release) it provides the means to shape a recognizable sound from a raw waveform. This technique can be used to synthesize the natural decay of a piano, or the sharp attack of a trumpet. It can be triggered by a keyboard or by another module in the system. Usually it drives the output of a VCA or VCF, but the patchable structure of the synthesizer makes it possible to use the envelope generator to modulate other parameters such as the pitch or pulse width of the VCO. Simpler EGs (AD or AR) or more complex (DADSR—Delay, Attack, Decay, Sustain, Release) are sometimes available.
  • LFO - A Low Frequency Oscillator is similar to a VCO but it usually operates below 20 Hz. It is generally used as a control voltage for another module. For example, modulating a VCO will create vibrato
    Vibrato is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms of two factors: the amount of pitch variation and the speed with which the pitch is varied .-Vibrato and...

     while modulating a VCA will create tremolo
    Vibrato is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms of two factors: the amount of pitch variation and the speed with which the pitch is varied .-Vibrato and...

  • RM - Ring modulator
    Ring modulation
    Ring modulation is a signal-processing effect in electronics, an implementation of amplitude modulation or frequency mixing, performed by multiplying two signals, where one is typically a sine-wave or another simple waveform. It is referred to as "ring" modulation because the analog circuit of...

     - 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.
  • S&H - Sample and hold
    Sample and hold
    In electronics, a sample and hold circuit is an analog device that samples the voltage of a continuously varying analog signal and holds its value at a constant level for a specified minimal period of time. Sample and hold circuits and related peak detectors are the elementary analog memory...

    , which takes a "sample" of the input voltage when a trigger pulse is received and "holds" it until a subsequent trigger pulse is applied. The source is often taken from a noise generator.
  • Sequencer
    Music sequencer
    The music sequencer is a device or computer software to record, edit, play back the music, by handling note and performance information in several forms, typically :...

    , which produces a sequence of notes, usually a music loop
    Music loop
    In electroacoustic music, a loop is a repeating section of sound material. Short sections of material can be repeated to create ostinato patterns...

  • 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
    Low-pass filter
    A low-pass filter is an electronic filter that passes low-frequency signals but attenuates signals with frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a high-cut filter, or treble cut filter...

  • Custom Control Inputs - Because modular synthesizers have voltage-driven inputs, it is possible to connect almost any kind of control. Pitch can be varied by room temperature if you wish, or amplification varied by light level falling on a sensor.

Modular synthesizers can be bulky and expensive, and there is a steep learning curve. Producing polyphonic music is painstaking and difficult, and, since patches cannot be saved, they are not easy to play live. In the late 1980s, modular synthesizers were largely replaced by highly integrated keyboard synthesizers, racks of MIDI
Musical Instrument Digital Interface
MIDI is an industry-standard protocol, first defined in 1982 by Gordon Hall, that enables electronic musical instruments , computers and other electronic equipment to communicate and synchronize with each other...

-connected gear, and sampler
Sampler (musical instrument)
A sampler is an electronic musical instrument similar in some respects to a synthesizer but, instead of generating sounds, it uses recordings of sounds that are loaded or recorded into it by the user and then played back by means of a keyboard, sequencer or other triggering device to perform or...

s. However, there continues to be a loyal following of musicians who prefer the physically patched approach, the flexibility and the sound of traditional modulars. Lately there has been a resurgence in the popularity of analog synthesizers; in fact, there are more manufacturers now than there were when they were at the height of their 1970's peak popularity.

Historic manufacturers of modular synthesizer hardware

The earliest commercial modular synthesizers were developed, in parallel, by R.A. Moog Co.
Moog Music
Moog Music is an American company based in Asheville, North Carolina which manufactures electronic musical instruments. The current Moog Music is the second company to trade under that name.-R.A. Moog Co. and the original Moog Music:...

, and Buchla
Buchla & Associates, Inc. is a manufacturer of electronic musical instruments, notably synthesizers and unique MIDI controllers. The 200e Electric Music Box and Lightning III are currently in production.-Buchla Music Box :...

 in 1963. The synthesizer both broadened the spectrum, and greatly eased the creation of electronic music
Electronic music
Electronic music is music that employs electronic musical instruments and electronic music technology in its production. In general a distinction can be made between sound produced using electromechanical means and that produced using electronic technology. Examples of electromechanical sound...

, which before was made via tape splicing, use of primitive electronic oscillators, and earlier electronic or electromechanical instruments such as the theremin
The theremin , originally known as the aetherphone/etherophone, thereminophone or termenvox/thereminvox is an early electronic musical instrument controlled without discernible physical contact from the player. It is named after its Russian inventor, Professor Léon Theremin, who patented the device...

 and the Ondes Martenot
Ondes Martenot
The ondes Martenot , also known as the ondium Martenot, Martenot and ondes musicales, is an early electronic musical instrument invented in 1928 by Maurice Martenot. The original design was similar in sound to the theremin...

ARP Instruments, Inc.
ARP Instruments, Inc. was an American manufacturer of electronic musical instruments, founded by Alan Robert Pearlman in 1969. Best known for its line of synthesizers that emerged in the early 1970s, ARP closed its doors in 1981 due to financial difficulties...

, Serge
Serge synthesizer
The Serge synthesizer is an analogue modular synthesizer system originally developed by Serge Tcherepnin at CalArts in the 1970s and originally produced by Tcherepnin's Serge Modular Music Systems company.Serge synthesizers have been used by composers such as Michael Stearns and Kevin Braheny The...

, and EMS
Electronic Music Studios (London) Ltd
Electronic Music Studios Ltd. is a synthesizer company formed in 1969 by Dr. Peter Zinovieff, Tristram Cary and David Cockerell....

 versions were soon to follow. In 1976, the Japanese company Roland
Roland Corporation
is a Japanese manufacturer of electronic musical instruments, electronic equipment and software. It was founded by Ikutaro Kakehashi in Osaka on April 18, 1972, with ¥33 million in capital. In 2005 Roland's headquarters relocated to Hamamatsu in Shizuoka Prefecture. Today it has factories in Japan,...

 came out with the Roland System 100. Also in the early 1970s, the mail-order electronics kit vendor Paia Electronics
PAiA Electronics
PAiA Electronics, Inc. is an American synthesizer kit company that was started by John Simonton in 1967. It sells various musical electronics kits including analog synthesizers, theremins, mixers and various music production units designed by founder John Simonton, Craig Anderton, Marvin Jones,...

 marketed two different lines of simple DIY modular synthesizer systems.

Modern manufacturers of modular hardware synthesizers (alphabetical)

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 internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

, the original patents having lapsed. Many hobbyist designers also make available bare PCB boards and front panels for sale to other hobbyists.

Form Factors

Many early synthesizer modules had modules with height in integer inches: 11" (e.g., Roland 100), 10" (e.g., Wavemakers), 9" (e.g., Aries), 8" (e.g., ARP 2500), 7" (e.g., Polyfusion, Buchla, Serge), 6" (e.g., Emu) and width in 1/4" inch multiples. More recently it has become more popular to follow the standard 19" Rack unit
Rack unit
A rack unit or U is a unit of measure used to describe the height of equipment intended for mounting in a 19-inch rack or a 23-inch rack...

 system: 6U (Wiard), 5U (8.75" e.g., Moog, Modcan), 4U (e.g., Serge). Two rack 3U unit systems in particular are notable: the Frac Rack system (e.g., Paia) and the similar Eurorack system (e.g., Doepfer). Further minor variations exist where European or Japanese manufacturers round a U measurement up or down to some closer convenient metric equivalent; for example the common 5U modules are exactly 8.75" (222.25mm), but non-American manufacturers may prefer 220mm or 230mm.


Other differences are with plugs that match 1/4-inch or 6.3mm jacks, 3.5mm jacks, and banana jacks, with main DC power supply (typically ±15 V, but ranging from ±18 V to ±12 V for different manufacturers or systems), with trigger or gate voltages (Moog S-trigger or positive gate), with typical audio signal levels (often ±5 V with ±5 V headroom), and with control voltages of volts/octave (typically 1 V/octave, but in some cases 1.2 V/octave.) Most analog modular systems use a volts/octave system, sometimes termed linear voltage control; some (such as Korg MS-20, ETI 4600) use a volts/hertz system with excellent temperature stability but less flexible control.

Modular software synthesizers (alphabetical)

There are also software synthesizers for personal computers which are organized as interconnectable modules. Many of these are virtual analog synthesizers, where the modules simulate hardware functionality. Some of them are also virtual modular systems, which simulate real historical modular synthesizers.
  • Alsa Modular Synthesiser http://alsamodular.sourceforge.net/
  • ARP 2600
    ARP 2600
    The ARP 2600 is a semi-modular analog subtractive audio synthesizer, designed by Alan R. Pearlman , and manufactured by his company, ARP Instruments, Inc...

     by Arturia
    Arturia is a software company located in Grenoble, France and founded in 1999 by Frédéric Brun and Gilles Pommereuil, both INPG-qualified engineers. The company's focus is on the development of electronic music software and tools - primarily emulation of vintage analog synthesizers...

  • AudioMulch
    AudioMulch is modular audio software for making music and processing sound. The software can synthesize sound and process live and pre-recorded sound in real-time....

  • Bidule
    Bidule is a commercial software application for the creation of interactive computer music and multimedia produced by the Canadian company Plogue Arts and Technology. It runs on both Windows and Mac computers....

     By plogue
  • ChucK
    ChucK is a concurrent, strongly timed audio programming language for real-time synthesis, composition, and performance, which runs on Mac OS X, Linux, Microsoft Windows, and iPhone/iPad. It is designed to favor readability and flexibility for the programmer over other considerations such...

  • CreamwareAudio Modular III
    CreamwareAudio Modular III
    CreamwareAudio Modular III is a modular synthesizer running on DSPs ,as part of the software environment provided for the Creamware 'Scope' line of sound cards....

  • Csound
    Csound is a computer programming language for dealing with sound, also known as a sound compiler or an audio programming language, or more precisely, a C-based audio DSL. It is called Csound because it is written in C, as opposed to some of its predecessors...

  • jMax
  • Jeskola Buzz
  • MaxMSP
    Max (software)
    Max is a visual programming language for music and multimedia developed and maintained by San Francisco-based software company Cycling '74. During its 20-year history, it has been widely used by composers, performers, software designers, researchers, and artists for creating innovative recordings,...

  • Kyma
    Kyma (sound design language)
    Kyma is a visual programming language for sound design used by musicians, researchers, and sound designers. In Kyma, a user programs a multiprocessor DSP by graphically connecting modules on the screen of a Macintosh or Windows computer.-Background:...

     by Symbolic Sound Corporation
    Symbolic Sound Corporation
    Symbolic Sound Corporation was founded by Carla Scaletti and Kurt J. Hebel in 1989 as a spinoff of the CERL Sound Group at the Computer-based Education Research Laboratory of the University of Illinois at Urbana-Champaign. Originally named Kymatics, the company was incorporated as Symbolic Sound...

  • Moog Modular V by Arturia
    Arturia is a software company located in Grenoble, France and founded in 1999 by Frédéric Brun and Gilles Pommereuil, both INPG-qualified engineers. The company's focus is on the development of electronic music software and tools - primarily emulation of vintage analog synthesizers...

  • Pure Data
    Pure Data
    Pure Data is a visual programming language developed by Miller Puckette in the 1990s for creating interactive computer music and multimedia works. While Puckette is the main author of the program, Pd is an open source project with a large developer base working on new extensions to it. It is...

  • Reaktor
    Reaktor is a graphical modular software music studio of proprietary license developed by Native Instruments. It lets musicians and sound specialists design and build their own instruments, samplers, effects and sound design tools. It is supplied with many ready-to-use instruments and effects, from...

  • RolloSONIC
  • SpiralSynthModular
  • SuperCollider
    SuperCollider programming language
    SuperCollider is an environment and programming language originally released in 1996 by James McCartney for real-time audio synthesis and algorithmic composition....

  • SynC Modular
  • SynthEdit
  • SynFactory
    SynFactory is a free and open source software synthesizer for Windows. It is based on the same sound generating principles such as subtractive synthesis as used in vintage modular synthesizers. Patches can be built from separate components and connected together with virtual patch cables...

  • SynthMaker
  • Tassman by Applied Acoustics Systems
  • Timewarp 2600 by Way Out Ware
  • Thor Polysonic Synthesizer (included with the current version of Propellerhead Reason)
  • Usine
    Sensomusic Usine is a Multitouch digital audio workstation used to manipulate, record and edit audio and MIDI in live situations.Usine is developed in Delphi by the French double bass player Olivier Sens, running on Microsoft Windows....

  • VAZModular

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 LED
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

s, software modular synthesizers offer the infinite variations and visual patching at a more affordable price and in a compact form factor.

The popular plugin formats such as VST
Virtual Studio Technology
Steinberg's Virtual Studio Technology is an interface for integrating software audio synthesizer and effect plugins with audio editors and hard-disk recording systems. VST and similar technologies use digital signal processing to simulate traditional recording studio hardware with software...

 may be combined in a modular fashion.

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 Synthi 100
The EMS Synthi 100 was a large analogue synthesizer made by Electronic Music Studios Ltd. It was released in 1971 and cost £6,500. It is estimated that fewer than 40 units were built....

, EMS VCS-3, ETI International 4600, Maplin 5600. The ARP 2500
ARP 2500
The ARP 2500, built from 1970 through the mid-70's, was ARP's first product. A monophonic analog modular synthesizer equipped with a set of sliding matrix switches above each module. These were the primary method of interconnecting modules. There were also rows of 1/8" miniphone jacks at the end...

 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
ARP 2600
The ARP 2600 is a semi-modular analog subtractive audio synthesizer, designed by Alan R. Pearlman , and manufactured by his company, ARP Instruments, Inc...

, Anyware Instruments Semtex, Cwejman S1, Korg MS-10
Korg MS-10
Korg MS-10 is an analogue synthesizer created by Korg in the mid to late 1970s. Unlike its bigger brother , the MS-10 only has one VCO per voice.The MS-10 is well known for its huge sounding electro bass sounds....

, MS-20
Korg MS-20
The Korg MS-20 is a patchable semi-modular monophonic synthesizer which Korg released in 1978 and which was in production until 1983. It was part of Korg's MS series of instruments, which also included the single oscillator MS-10, the keyboardless MS-50 module, and the SQ-10 sequencer...

, MS-50, PS-3100, PS-3200 and PS-3300
Korg PS-3300
The Korg PS-3300 is a polyphonic analog synthesizer produced by Korg, between 1977 and 1981.- History :The Korg PS-3300 is one of the biggest and rarest synthesizers ever made. Only around 50 units were produced by Korg over a 4-year period from 1977 to 1981 after which it was discontinued...

, Mungo Enterprises State Zero, and Roland System-100
Roland System-100
The Roland System 100 was an analog semi-modular synthesizer manufactured by Japan's Roland Corporation, released in 1975 and manufactured until 1979....


Electronically Reconfigurable Systems

Reconfigurable systems allow certain signals to be 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:
  • Arturia Origin by Arturia
    Arturia is a software company located in Grenoble, France and founded in 1999 by Frédéric Brun and Gilles Pommereuil, both INPG-qualified engineers. The company's focus is on the development of electronic music software and tools - primarily emulation of vintage analog synthesizers...

    , self contained digital modular synthesizer.
  • Clavia Nord Modular
    Clavia Nord Modular
    The Clavia Nord Modular series is a line of synthesizers produced by Clavia, a Swedish digital synthesizer manufacturer. The Nord Modular series, in common with their sister range the Nord Lead series, are analogue modelling synthesizers, producing sounds which approximate those produced by...

     and Clavia Nord Modular G2 by Clavia
    Clavia Digital Musical Instruments is a Swedish manufacturer of virtual analog synthesizers, virtual electromechanical pianos and stage pianos, founded in Stockholm, Sweden in 1983 by Hans Nordelius and Mikael Carlsson.-The Company:...

    , these are however 100% digital modular synthesizers.

External links