The company say that concept for the Four Strings Series originated from the desire to incorporate physical strings into Eurorack and offer something similar to a lap steel guitar or dulcimer that can be seamlessly integrated into any Eurorack frame. They decided to design a system without a fretboard, however, with the aim of allowing space for users to place other modules and contraptions underneath the strings.

First to make it off the drawing board were headstock and bridge units, which were followed by a humbucker module designed to capture the strings’ sounds just like an ordinary electric guitar. The company say that the limitations of standard humbuckers lead to them developing their our own pickup, using a quadraphonic configuration that provides a discrete pickup for every string, allowing for independent string volume control. 

ADDAC120 Headstock & Bridge
This is the base of the String modules, a Headstock & Bridge module that can accommodate string gauges up to 0.055 — users can make these holes larger if they wish to fit heavier strings. Both panels are 2mm stainless steel for strength. The headstock features four locking tuners for easier string installation.

ADDAC121 Humbucker
This is the simple Humbucker pickup module. It features Tone and Volume controls as well as a Low/High gain switch for introducing some saturation. An integrated preamp brings the volume up to synth level. The height of the pickup can be adjusted using the mounting screws, and can be removed and used by hand.

ADDAC122 Quadraphonic Pickup
The Quadraphonic Pickup combines four independent pickups each with their own preamp, volume control and output jack. A Mono Mix output (post-volume) is also available. All outputs are synth level, and the height of the pickup can be adjusted using the mounting screws.

ADDAC124 Plectrums
The Plectrum module features a servo per string, allowing each string to be plucked independently either via the module’s dedicated push-buttons, incoming triggers or MIDI. In Pluck mode, the servo will move about 20 degrees; in Harmonic Mode the servo only moves about 10 degrees before stopping at a vertical position and lightly tapping the string to produce harmonics.

ADDAC125 Strings Mute
This module is inspired by the Mute system found in some of Fender’s Jaguar and Bass VI guitars, where a piece of foam can be engaged to press against the string dampening their natural vibration. The module employs a servo motor that raises and lowers a piece of foam, which when pressed against the strings lightly dampens their natural vibration. While not as effective as a standard palm mute, it allows a different tone to be automated.

ADDAC126 Rotary Exciter
The Rotary Exciter features a 7000 RPM brushless motor that rotates a surface with four magnets with opposed magnetic poles, inducing a rotating magnetic field that will force the strings to vibrate whenever the rotational speed matches the frequency or harmonics of any of the strings’ tunings.

ADDAC127 EBow Slider
This module creates a harness and a sliding mechanism for a standard EBow. It allows the user to slide the EBow back and fourth below the strings. The EBow used features the PianoBow modification where we sand off the EBow’s feet so that it can get closer and avoid touching the strings when sliding it back and fourth. The height of the EBow can be raised or lowered using the four thumb screws.

Bow Arch Attachment
This attachment raises the two middle strings, allowing a bow to reach each string individually.

Small Resonators
Although quite simple, these are extremely effective adding harmonics to non-wounded strings. For every resonator attached to the string a new partial is added, placing more pieces adds more partials which makes the tone increasingly complex. The tuning of each harmonic is defined by the position of the resonator on the string — the resulting sound can be quite surprising, and very much resembles a bell-type sound.

ADDAC120F Strings Frame
This is a custom-built frame designed specifically for the ADDAC12X String modules.