Eurorack modular synthesizers have become increasingly popular over the past decade. After COVID, I became interested in having FaMLE begin usinging these extremely hands-on systems for programming music. One downside of Eurorack systems is cost, and since I wanted to build multiple systems for ensemble use, I leaned into creating DIY utility modules.

Mult

The most common utility module is a multiple (mult). This module takes a single signal and splits it to multiple destinations. Because these modules are passive, any jack can function as the input, and markings or colors typically indicate which jacks are connected.

Switch Mult

Switches allow an input signal to be routed to one of two or three destinations. In many of my designs, switches and multiples are combined into a single module.

Or-Gate

Generally, multiples are for splitting 1 input to multiple outputs rather than adding inputs together. An Or-Gate is a simple way of mixing signals together, generally only suitable for adding trigger signals together and generating a high output whenever any of the inputs are high.

Attenuators

Attenuators are a really useful way of scaling the level of a control signal. Really, these are kind of simple volume knobs which are useful for both audio and control signals.

Filters

Passive high-pass filters are also extremely useful. They can remove low frequencies from an audio signal or convert a gate signal into a trigger.

Envelope Generator

Envelope generators create amplitude envelopes to control synthesizer parameters. One module I designed provides two related envelopes with shared attack and decay controls, plus a ratio control that scales the length of the second envelope relative to the first. Unlike the previous module, this one uses an Arduino Micro as the envelope generator.

Quantizer

An especially practical module is a pitch quantizer, which converts continuous voltage into discrete musical pitches. My quantizer design constrains pitches to a scale and allows transposition between different modes. One input handles pitch quantization, while a second input transposes the melody by scale degrees.