lyra-drone-synth-norns

Lyra-Drone-Synth-Norns (WIP)

Note: This is a Work in Progress! Currently in the early stages of building a SuperCollider engine, with plans to build a Monome Norns + Grid application around it.

Concept

This project is an experimental drone synthesizer heavily inspired by the "organismic" architecture of the Soma Laboratory Lyra-8. Instead of standard polyphony, it focuses on 8 interconnected oscillators that can continuously bleed into and modulate one another, creating massive, chaotic, and evolving textures.

Architecture (The SuperCollider Engine)

The engine is built as a single, monolithic SynthDef (\lyra_core) rather than spawning new synths for every voice. This mimics a hardware device being constantly "on".

1. The Voices

• 8 Oscillators: Powered by VarSaw, with the width parameter slowly modulated by LFNoise2 for an organic, analog-drifting feel.
• Envelopes & VCA: Uses Env.asr. Each voice has a gate (for grid touch plates) and a hold (for continuous drone).
• Fast/Slow Release: Each voice has a toggle (relSwitches) to switch between a quick, percussive release (0.3s) and a long, ambient fade-out (6.0s).

2. The Cross-FM Matrix

The core of the sound design is the feedback frequency modulation (Cross-FM) between oscillator pairs: (1&2), (3&4), (5&6), and (7&8).

To achieve this in digital DSP the SuperCollider UGens LocalOut.ar and LocalIn.ar are used:

• LocalOut.ar / LocalIn.ar: The raw oscillator outputs are sent to LocalOut, and read back via LocalIn on the next audio sample (a ~1.5ms delay). This solves the circular dependency problem where Voice 1 and Voice 2 need to know each other's current state simultaneously.

The actual cross-wiring is done via array indexing, which swaps the routing so Voice 1 is modulated by Voice 2, Voice 3 by Voice 4, and so on.:

var modulators = feedbackIn[[1, 0, 3, 2, 5, 4, 7, 6]];

3. The Hyper LFO (Chaotic Modulation)

The engine features a "Hyper LFO", a complex low-frequency generator that produces chaotic modulation.

• The Concept: It consists of two separate triangle wave LFOs (LFO A and LFO B) running at different base frequencies.
• Cross-Modulation: Using a dedicated control-rate feedback loop (LocalIn.kr and LocalOut.kr), the output of LFO A modulates the speed of LFO B, and vice versa.
• The Result: The lfoCrossMod parameter dictates how aggressively they pull each other off the rails. When turned up, the resulting summed waveform (hyperLfo) stops being a repeating pattern and turns into an organic, drifting, and unpredictable "breathing" motion. This is fed into the oscillators via lfoPitchDepths to create an unstable, living pitch drift.

4. Safety Mechanisms

Heavy feedback FM can easily cause math errors or silent crashes. This engine includes two safety nets:

• LeakDC.ar inside the loop: Heavy FM with asymmetrical waveforms creates a DC offset (the wave gets stuck above or below 0). If fed back into the FM loop, this offset multiplies endlessly. LeakDC scrubs the signal clean before it goes back into LocalOut.
• Frequency .clip(10, 15000): Prevents the FM matrix from driving the oscillator frequency into negative values or above human hearing.

Next Steps (Roadmap)

• Dual Modulated Delay: Build a PT2399-style dual delay network that can be modulated by the raw audio of the oscillators themselves.
• Norns Lua Script: Map the SuperCollider parameters to the Norns screen, encoders, and Monome Grid.