Modular synthesizer

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 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
• ENV or ADSR - Envelope generator[?], which is used to modulate an VCA to chane the volume of the sound to simulate the volume contour of natural sounds. Because of the modular nature of the synthesizer the Envelope can also modulate 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