Modular synthesizers are synthesizers composed of separate modules for different functions. The modules can be connected together by the user to create a patch. The outputs from the modules may include audio signals, analog control voltages, or digital signals for logic or timing conditions. Typical modules are voltage-controlled oscillators, voltage-controlled filters, voltage-controlled amplifiers and envelope generators.
The first modular synthesizer was developed by German engineer Harald Bode in the late 1950s.The 1960s saw the introduction of the Moog synthesizer and the Buchla Modular Electronic Music System, created around the same period.The Moog was composed of separate modules which created and shaped sounds, such as envelopes, noise generators, filters, and sequencers,connected by patch cords. The Japanese company Roland released the Roland System 100 in 1975, followed by the System 700 in 1976 and the System 100m in 1979.
Moog actively sought advice from musicians, resulting in groundbreaking ideas like the ADSR envelope generator, pitch and modulation wheels and, most importantly, the inclusion of a familiar organ-style keyboard. But others believed that such contrivances were concessions to convention, and therefore anathema to the idea of a truly forward-thinking instrument. Donald Buchla was of that opinion, and championed the use of alternate controllers.
There are now more choices than ever before, both physical and virtual, with the latter shod of the size and expense of 'real' machines. Software modular systems have grown in capability and power, and continue to do so, all the while becoming more user and CPU-friendly. As processing power increases, the software modular now eclipses that of its hardware counterpart. Once, software systems such as SynC Modular and Generator (eventually renamed Reaktor!) offered limited real-time capabilities, but such limitations no longer apply in any practical setting.
SOURCE 1: Modular Synthesizer - Wikipedia (External) | SOURCE 2: A Brief History of Modular Synthesis (External)