User:Borinwithnog/Eurorack

Voltage-Controlled Oscillators (VCOs)
The most common source of sound in any modular synthesizer is a Voltage-Controlled Oscillator. They depend on a Control Voltage, a lot of times routed from external hardware (for example, an analog synthesizer with a CV output, or MIDI signals processed on a MIDI-to-CV converter), to both control pitch, and output different waveforms.

There are various Control Voltage standards for determining the Voltage/Pitch relationship. The most popular ones are (1) Volts-per-octave, where 1 V equals one octave, and (2) Hertz-per-Volt, where each octave equals doubling or halving the voltage.

Noise Source
They still under the category of source modules, these modules are responsible for producing different “types” of noises (or colors). They can output (1) white noise — where all frequencies in the spectrum are equally powered, (2) pink noise — where there is more power to the lower end, due to its logarithmic nature, (3) brown noise — similar to pink noise, but steeper slope, (4) blue noise — oversimplified, the opposite of the pink noise, with more power concentrated on the higher frequencies, among others.

Modulators
Under the category of processors, modulators will modify an incoming signal. The effects produced are widely varied and a lot of times, modules will be built for a specific function, for example:


 * LFOs (Low-Frequency Oscillators) will produce a inaudible frequency (usually below 20Hz), that will be used to modulate the VCO, and produce a vibrato-like effect by varying the pitch.
 * Tremolos will affect the loudness of a signal producing a similar effect of the LFOs.

Filters
Another kind of processor, filters are modules shaping the sound by attenuating specific frequency ranges. These modules will contain all or a selection of the following: (1) a high-pass filter (where anything above a certain frequency can “pass”), (2) a low-pass filter (anything below a given frequency can pass), (3) a band-pass filter (where anything “in between” two frequencies can pass), and (4) a notch filter (where one cuts a specific range of frequencies out allowing everything else to pass).

Sequencers
Essentially, modules that can both operate as a source or a processor of musical content in the form of CV or MIDI messages. The most common kind are step-sequencers, where each individual musical event is triggered in a “step” of a bigger sequence (or loop).

Utilities
Utility modules are the ones responsible for expanding certain capabilities of a specific setup. They can be used to combine, split, divide, multiply, quantize, or offset a signal. One example of a utility module is a multiplier, that allow one to send any CV output to many other inputs. Another example are the attenuators responsible for scaling the CV signal with a control knob (much like faders in a mixing console).

Effects
A lot similar to the concept in a guitar pedal, effects modules are used to change the sound of an incoming signal. They can be (1) dynamic processors, used to control the level of a signal (like compressors, or limiters), (2) equalizers, used to change the frequency characteristics of a given sound (sometimes in the form of a eurorack mixer module), or (3) special effects, like delays, reverbs, or choruses.