ADDAC303 Muscle Sensing

Name: ADDAC System Sensing
Brand: ADDAC System

This Eurorack module turns muscle flexes into control voltage, so your body becomes the synth interface.

Overview

The ADDAC303 Muscle Sensing is a bridge between your nervous system and your modular rig. ADDAC System of Lisbon, Portugal built it as a compact 4 hp Eurorack module that uses electrode pads to detect muscle tension and turn physical movement into usable control signals. It belongs to the ADDAC300's Expressive Controls Series, a line focused on expanding how we interact with modular systems beyond knobs and keyboards. Instead of playing notes, you clench a fist, tap a foot or tense a forearm, and that gesture shapes sound in real time.

It's a legitimate, if niche, performance tool. The module ships with reusable electrode pads, so it's ready to go out of the box. Stick them on your arm, flex, and you've got an envelope. Pair it with a drum module and it's an organic trigger source - raw, human and slightly unpredictable. One user noted it's "good for drums, probably bad/limited for flute unless you were tapping your foot along," which sums up its strengths and limits neatly. It doesn't read fine motor control. It reads effort. That makes it better suited for rhythmic or gestural expression than melodic precision.

ADDAC had already released the ADDAC307 Heart Sensing module before this, which they called "the second module we make to take advantage of the physical body as a control source." That implies the Muscle Sensing was the first. Most modular gear is about precision and repeatability, and ADDAC went the other way, into the messy, variable nature of the human body. The Muscle Sensing, along with the Light to CV and Heart Sensing modules, forms a suite for "greater expression and sonic exploration," as described by users and the manufacturer alike.

Specifications

Manufacturer	ADDAC System
Product type	Eurorack module
Width	4 hp
Depth	4 cm
Max current	60ma
Bus board cable	8 × 2 idc (doepfer style) connector
Output voltage range	±10v
Offset range	±10v

Key Features

Body as interface

The idea is simple. Attach electrode pads to your skin and flex a muscle, and you generate a bio-signal that the module converts into control voltage. This isn't MIDI aftertouch or a ribbon controller. It's direct physiological input. The signal path starts with raw muscle activity, which the module conditions into a usable envelope.

Envelope shaping and smoothing

Once the signal is captured, the module gives you hands-on control. The gain knob adjusts sensitivity - how much flex translates to how much voltage. The offset knob shifts the baseline, which sets the resting level of the CV output. A smooth switch toggles between hard and soft smoothing of the raw sensor output. That lets you shape the response: a sharp, percussive envelope for drum triggers, or a slower, more gradual rise for filter sweeps or volume swells.

Dual CV and gate outputs

The ADDAC303 provides both a positive and an inverted CV output, so the same muscle movement can open one parameter while closing another - say, brightening a filter while darkening a second oscillator. It also has a comparator gate output with an adjustable threshold knob. This turns a muscle flex into a digital on/off signal, useful for triggering sequencers, drum modules or sample players. Set the threshold high and only strong clenches will fire it. Set it low and even subtle twitches can trigger events.

Designed for performance

The module ships with reusable, replaceable electrode pads, so you can swap them out when they wear down or reposition them mid-performance. Stick them on your arm to trigger beats, on your leg to tap tempo, or even on another musician in the band, so a drummer's hit or a bassist's pluck becomes a control signal. Perfect Circuit calls it "perfect as a non-traditional interface for your modular."

Historical Context

The ADDAC303 Muscle Sensing was the first module in ADDAC System's push toward body-driven control. It preceded the ADDAC307 Heart Sensing, which the company later described as their second module "to take advantage of the physical body as a control source." That makes the Muscle Sensing the first in their Expressive Controls Series, a line that also includes the ADDAC308 Light to CV. Together, these modules shift away from traditional control methods and treat environmental and biological inputs as valid sources of musical expression.