What is the analog modular synthesizer?

The analog 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 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.

In general, when introducing modular synth, the selection of modules for assembling the system is an important event before purchase, and it is the real pleasure of modular synth. But for beginners of analog modular synthesizer, it will be the first major hurdle. Choosing a module yourself is a very difficult problem unless you understand what you need and what you want, clear vision and knowledge. Therefore, I will explain the basic knowledge of the sound source circuit, the circuit in charge of the control signal, and the control standard.

Configuration of the sound source circuit
The analog modular synthesizer is composed of the following circuits.

A circuit in charge of an audio signal
The three functions in charge of the audio signal are as follows.

VCO
Abbreviation for the voltage controlled oscillator. An oscillator that creates a basic waveform.

VCF
Abbreviation for the voltage-controlled filter. A circuit for processing waveforms.

VCA
Abbreviation for voltage controlled amplifiers. A circuit for controlling volume.

A circuit in charge of a control signal
The main circuits for controlling the above three functions are as follows.

Envelope Generator
A circuit that generates a voltage that varies with time by four parameters: Attack / Decay / Sustain / Release (Reverberation).

LFO
Abbreviation for low-frequency oscillator. Send a low frequency as a control signal to the control circuit of the audio signal, giving a periodic change (For example, if you send it to the VCO, you can create a vibrato).

Keyboard or Sequencer
Function to input performance information.

Control Standard
An analog modular synthesizer roughly controls each function by sending and receiving two types of information as to voltage.

GATE
Signal on/off information. Control the length of the sound.

CV
Abbreviation of controlled voltage. Control the value of each function, beginning with the interval.

In the case of a modular synthesizer, it is possible to more flexibly modulate the audio signal with a patch cable.