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The modular synthesizer is a type of synthesizer, which exists in both physical and virtual forms, consisting of separate specialized modules. The specialization is usually in the module being designed to allow the modification or processing of one parameter of a signal, such as the frequency (oscillator), spectrum (filter), or amplitude (amplifier). The modules are not hardwired together but are connected together with patch cords, a matrix patching system, or switches to create a patch. The voltages from the modules may function as (audio) signals, control voltages, or logic conditions.
There exist many different types of modules. There are basic modules, and compound modules, a compound module being a single module made up of several basic modules internally wired together. Examples of compound modules include the envelope follower, sequencer, and vocoder. Modules with the same basic functions may have different inputs, outputs and controls, depending on their degree of complexity. Some examples include the VCO, which may have options for sync (hard or soft), linear or exponential frequency modulation, and variable waveshape; the VCF that may have both resonance and bandwidth controls; and the envelope follower which may provide outputs at each stage of the process. 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.
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:
Modular synthesizers can be 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,[when?] 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 MAX/MSP, Pd and Reaktor etc.
The 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. 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. ARP (in 1970), Serge (1974), and EMS (1969) versions were soon to follow.
Japanese company Roland released the Roland System 100 in 1975, followed by the Roland System 700 in 1976. Also in the 1970s, there were at least two mail-order electronics kit vendors Paia Electronics, 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. 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).Joseph A. Paradiso's Massive Modular Synth is among the world's largest home-designed and built synthesizers.
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.
Many early synthesizer modules had modules with 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.
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 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.
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.
A 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.
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.
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, Cwejman S1, EML101, Evenfall Minimodular, Future Retro XS, Korg MS-10, MS-20, MS-50, PS-3100, PS-3200 and PS-3300, Mungo Enterprises State Zero, Roland System 100 and Moog Mother-32 .
Hybrid synthesizers use hardware and software combination. In alphabetical order: