The modular synthesizer is an early type of synthesizer consisting of separate modules which must be connected by wires to create a so called patch. These synthesizers are very flexible. Instead of audio, every output generates a voltage (or a current). All inputs expect a voltage, so that almost any combination of connections between the modules is allowed and valid.

There exist many different modules and even the modules with the same function have different inputs and output on various models. But there are some standards which manufactures followed for their range of synthesizers. Connecting synthesizers from different manufactures often requires converters however.

Some standard modules found on almost any modular synth are:

• VCO - Voltage Controlled Oscillator, which will play a note in a simple waveform (most usually a square wave or a sawtooth wave)
• VCF - Voltage Controlled Filter, which filters out all sounds above or below a certain frequency
• VCA - Voltage controlled amplifier, which controls the amplitude or overall volume
• ADSR - Envelope generator that is used to modulate a VCA to change the overall volume of the sound. This simulates the volume contour of natural decaying sounds like a piano. The modular structure of the synthesizer makes it possible to use the envelope generator for modulating other parameters like the cutoff frequency of the filter, so the timbre of the sound can be changed while the sound progresses.
• LFO - Low Frequency Oscillator, from which the output is a low frequency waveform, most usually a sine or triangle wave, usually used as a control for some other module (for instance, to modulate the frequency of the VCO's output)
• Sample and hold, which takes a snapshot of the input voltage on a trigger pulse and keep it steady even when the input voltage changes.
• Sequencer, which produces a sequence of notes, usually a music loop

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 and flexibility of traditional modulars.

Modern manufacturers of modular synthesizer hardware (alphabetical)

• Analogue Solutions (Concussor )
• Analogue Systems (RS Integrator )
• Blacet Research
• Cyndustries
• Doepfer Musikelektronik (A-100 )
• Modcan
• Oakley Sound Systems
• Sound Transform Systems (Serge)
• Synthesis Technology (MOTM )
• Synthesizers.com
• Wiard Synthesizer Company

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 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.

Modular synthesizer software (alphabetical)

• CreamwareAudio Modular III
• Csound
• jMax
• MAX/MSP
• Moog Modular V by Arturia
• pure data
• Reaktor
• SpiralSynthModular
• SuperCollider
• SynFactory

External links

• 120 years of Electronic Music has information on classic modular synths.
• Vintage Synth Explorer - information on vintage synth gear, including Moog and other modular synths.
• Synthmuseum.com
• Modular Analog Synthesizers Return! - article about new modular synstems.
• Current listing of analog synthesizer manufacturers
• Using the Moog modular synthesizer
• Sound samples from classic synthesizers like the Moog Modular