Modular synthesizers are synthesizers composed of separate modules of different functions. The modules can be connected together with patch cords, a matrix patching system, or switches by the user to create a patch. The output (voltages) from the modules may function as (audio) signals, control voltages, or logic/timing conditions. Typical modules are oscillators (operate on frequency), filters (spectrum), amplifiers/gates (amplitude) and Envelope generators (dynamic control).
Types of modulesThe basic modular functions are: signal, control, logic/timing. Typically, inputs and outputs are an electric voltage.
The difference between a synthesizer module and an effects unit is that an effects unit will have sockets for input and output of the audio signal and knobs or switches for the musician to control various parameters of the device (for example, the rate of a chorus pedal) while a synthesizer module may have sockets for input and output, but will also have sockets so that the device's parameters can be further controlled by other devices/modules (for example, to connect an external Low Frequency Oscillator to a delay module to get the chorus effect.)
There exist many different types of modules. Modules with the same basic functions may have different inputs, outputs and controls, depending on their degree of complexity. Some examples include the Voltage Controlled Oscillator (VCO), which may have options for sync (hard or soft), linear or exponential frequency modulation, and variable waveshape; the Voltage Controlled Filter (VCF) that may have both resonance and bandwidth controls; and the Envelope Follower which may provide outputs at each stage of the process. Examples of more complex modules include the frequency shifter, sequencer, and vocoder.
There are some standards which manufacturers followed for their range of physical synthesizers, such as 1V/octave control voltages, and gate / trigger thresholds providing general compatibility; however, connecting synthesizers from different manufacturers may require cables with different kinds of plugs.
In the past, modular synthesizers were often bulky and expensive. Due to the continuously variable nature of knobs and sliders, reproducing an exact patch can be difficult or next to impossible. In the late 1970s, modular synthesizers started to be largely supplanted in pop music by highly integrated keyboard synthesizers, racks of MIDI-connected gear, and samplers. However, there continued to be a community who chose the physically patched approach, the flexibility and the sound of traditional modular systems. Since the late 1990s, there has been a resurgence in the popularity of analog synthesizers aided by physical standardization practices, an increase in 'retro' gear and interest, decreased production costs and increased electronic reliability and stability, the rediscovered ability of modules to control things other than sound, and a generally heightened education through the development of virtual synthesis systems such as VCV Rack, MAX/MSP, Pd and Reaktor etc.
Typical modulesModules can usually be categorized as either sources or processors
Some standard modules found on almost any modular synthesizer are:
Sources - characterized by an output, but no signal input; it may have control inputs:
Processors - characterized by a signal input and an output; it may have control inputs:
Historic manufacturersThe earliest commercial modular synthesizers were developed, in parallel, by R. A. Moog Co., and Buchla in 1963. Their designs drew from innovations by inventor Hugh Le Caine, particularly his implementation of control voltage in the electronic sackbut. Moog was also influenced by the sequencers of Raymond Scott. Buchla was influenced by his work on analog computers. 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 the Ondes Martenot. EMS (1969), ARP (1969), EML(1969), Wavemakers (1971), E-mu (1971), Serge (1972), Aries and Polyfusion (1975) versions were soon to follow.
Japanese company Roland released the Roland System 100 in 1975, followed by the Roland System 700 in 1976, and the Roland System 100m in the early 1980s.
Also in the 1970s, there were at least three mail-order electronics kit vendors Paia Electronics, E-mu, and Aries, marketing different lines of simple DIY modular synthesizer systems. The Aries system was modeled on the circuits produced by Bernie Hutchins and published as Electronotes. A large pin-matrix synthesizer, the ETI 4600, was offered in kit form from 1973 in the Australian Electronics Today International (ETI) magazine. In the UK in the 1980s the Digisound 80 Modular Synthesizer, designed primarily by Charles Blakey, was sold as a kit by the company Digisound Ltd. Many of the early modules appeared in the early to mid-1980s as construction articles in two British electronics magazines - Electronics Today International (ETI) and Electronics & Music Maker (E&MM).
As well as manufactured synthesizers, there have been notable bespoke systems created for personal or academic use with no intention of becoming a product, for example the SalMar Construction of Sergio Franco . Joseph A. Paradiso's Massive Modular Synth is among the world's largest home-designed and built synthesizers.
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 original patents having lapsed. Many hobbyist designers also make available bare PCB boards and front panels for sale to other hobbyists.
Form FactorsMany early synthesizer modules had modules with [http://www.synthesizers.com/formfactors.html height] in integer inches: 11" (e.g., Roland 700), 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 system: 6U (Wiard), 5U (8.75" e.g., Moog/Modcan), 4U (e.g., Serge), 3U (Eurorack).
Two 3U unit standards in particular are notable: Frac Rack (e.g., Paia), which uses the entire 3U for the front panel, and Eurorack (e.g., Doepfer) which has a 2mm horizontal lip that the front panels are seated between. 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.
ElectricalOther differences are in the plugs used, which can match 1/4-inch or 6.3mm jacks, 3.5mm jacks, banana jacks, or breadboard patch leads, in the main power supply, which is most often ±12 V or ±15 V, but can range from 2.5±2.5 V to 0±18 V for different manufacturers or systems, in the 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 system in which the frequency is exponentially related to the pitch (such as 1 volt/octave or 1.2 volts/octave), sometimes called "linear" because the human ear perceives frequencies in a logarithmic fashion, with each octave having the same perceptual size; some synthesizers (such as Korg MS-20, ETI 4600) use a volts/hertz system, where the frequency (but not the perceived pitch) is linear in the voltage.
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.
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.
The popular plugin formats such as VST may be combined in a modular fashion.
Semi-modular synthesizersA modular synthesizer has a case or frame into which arbitrary modules can be fitted; 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, an instrument. 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 and often to connect external components or modules (chosen and supplied by the user) between those of the instrument.
Matrix SystemsMatrix systems use pin matrices or other crosspoint switches rather than patch cords. The ARP 2500 was the first synthesizer to used a fixed switch matrix. The pin matrix was made popular in the EMS VCS-3 and its descendants like the EMS Synthi 100. Other systemss include the ETI International 4600, and the Maplin 5600.
In digital times the clean logical layout of these matrices has inspired a number of manufacturers like Arturia to include digitally programmable matrices in their analog or virtual analog synthesizers. Many fully digital synthesizers, like the Alesis Ion, make use of the logic and nomenclature of a "modulation matrix", even when the graphical layout of a hardware matrix is completely absent.