Making the Guitar Shine in a Modular System: Best Notes, Chords, and Electroacoustic Principles

Whether we’re seasoned guitarists or simply curious about new sonic possibilities, plugging a guitar into a modular system can unlock a world of fascinating sounds. The interaction between the harmonic richness of the guitar and the circuitry of a modular synth often yields textures that are tough to recreate any other way. In this blog post, we’ll explore:

Which notes and chords best highlight a modular setup
How these choices interact effectively with our modules
A few electroacoustic concepts to help us optimize and expand our final sound

1. Key Chords and Notes to Bring Out the Best in a Modular System

a) Open Chords

Open chords—like C major, G major, D major, or A minor—stand out because they include open strings that resonate freely, producing a wide range of harmonics. When we feed these harmonics (directly or through a preamp) into our modular’s audio input module, we give the filters, wavefolders, and other processors plenty of high-frequency content to work with.

Why this matters:
Modules designed for signal processing (e.g., a VCF or a wavefolder) come alive when presented with the extra harmonic detail produced by open strings. This results in a richer palette of sounds and more organic modulation options.

b) Dissonant Intervals (Diminished Fifths, Sevenths, Ninths)

Dissonant chords or more complex voicings (such as Bdim7 or G7(b9)) create stronger “beats” between frequencies. These are slight phase offsets that lead to natural modulation in our sound—a phenomenon especially noticeable in a modular environment.

Example of practical use:
- Strum a G7(b9) chord with a staccato attack.
- Route that signal into a ring modulator or a frequency shifter.
- We’ll hear metallic, shifting textures driven by the natural dissonances in the chord.

c) Natural Harmonics on the Guitar

By lightly touching the string over the 12th, 7th, or 5th fret, we can produce natural harmonics that are perfect for modular processing.

Why it works:
Natural harmonics emphasize precise frequencies (like the octave, fifth, etc.) that modules such as an envelope follower can easily track. We can even use these harmonics to trigger envelopes or sequence events in the modular.

2. The Role of Modules in Our Signal Chain

a) Preamp or Instrument Input Module

Before anything else, it’s essential to have a dedicated module or interface (e.g., Expert Sleepers ES-9, ALM Busy Circuits SBG, etc.) that converts our guitar-level signal to modular-level voltage (±10V in Eurorack). Without proper gain staging, our signal might be too weak or noisy to get the most out of the modular.

b) The Envelope Follower

Many modular systems include an envelope follower, which converts the amplitude of an audio signal into a control voltage (CV). Strum harder, and the voltage goes up—this can modulate a filter, VCA, or oscillator.

Example:
- We play an open G chord.
- The envelope follower detects the volume spike and slowly opens a VCF (Voltage-Controlled Filter).
- The result is a filter sweep that follows the natural dynamics of our guitar playing.

c) Processing Modules (VCF, Wavefolder, Ring Modulator, Delay, etc.)

VCF (Voltage-Controlled Filter): Great for sculpting the harmonics of open chords.
Wavefolder: Folds and enriches waveforms, especially when fed chords with complex harmonics.
Ring Modulator: Produces metallic or “cosmic” tones, especially when paired with dissonant chords.
Delay/Echo: A modular delay (e.g., Chronoblob, Mimeophon, etc.) can add depth, spaced-out repeats, and unpredictable feedback synced to our picking or strumming.

d) Reinjection (Feedback Loops)

Another major benefit is setting up feedback loops. For instance, we can send the processed signal out to an amp, re-mic it, and feed it back into the modular. This controlled feedback loop emphasizes certain frequencies and expands our ambient texture.

3. Electroacoustic Notions to Optimize Our Sound

a) Fundamental Frequencies and Harmonics

When we strum a guitar chord, the fundamental note and its higher harmonics (2nd, 3rd, 4th, etc.) create a rich spectral content. Filters, resonators, or ring modulators in a modular system thrive on this complexity, as they have more frequency “material” to work with.

b) Beats

Beats occur when close frequencies overlap. For example, a diminished fifth (tritone) creates slight frequency shifts that a resonant VCF or a phaser can amplify. This gives us evolving, dynamic modulations that can feel unpredictable yet musical.

c) Dynamic Envelopes and Room Reverb

If we’re playing in an acoustic space—like a concert hall or a home studio with natural reverb—then the room’s decay can enrich the signal before it even hits the modular. Experiment with:

Close-miking for a dry, tightly controlled sound.
Distance miking for a more ambient, reverberant tone.

Conclusion: An Endless Playground

Guitars, with their harmonic richness, are perfect for feeding a modular system. By carefully choosing our chords—open chords for extra harmonic content, dissonant intervals for pronounced beats, and natural harmonics for pure, clean signals—we can maximize the interplay between strings and circuits. Our modules (preamp, envelope follower, VCF, wavefolder, ring modulator) then elevate these sounds into uncharted territory.

The possibilities are limitless: we can mix in external stompboxes, create feedback loops, or even modulate oscillator pitch in real time with the guitar signal. Each attempt yields a new texture or color.