Making an Electronic Sound Sculpture - Eirik Brandal

The video documents building a self‑generating electronic sound sculpture and uses it to explain practical algorithmic composition, synthesis, and hybrid analog–digital design.[youtube]​

Concept and composition

• The piece is a sound sculpture that generates music in real time from about 800 lines of microcontroller code, with no external performance input.[youtube]​

• He frames this as algorithmic composition: sets of rules and stochastic processes that produce non‑deterministic music within constraints defined by the composer.[youtube]​

• He contrasts historical rule‑based counterpoint (four‑part harmony built from strict rules) with modern computer music, where the computer itself performs the algorithm rather than humans interpreting a score.[youtube]​

Sound and synthesis fundamentals

• He breaks a musical sound into pitch, duration, amplitude, and timbre, grouping them as spectral, temporal, and dynamic dimensions that an algorithm can control.[youtube]​

• He briefly critiques traditional Western notation as a “lattice” that cannot fully represent complex timbres and gestures, referencing Trevor Wishart’s work on sonic morphology.[youtube]​

• He outlines subtractive synthesis (filtering partials from rich waveforms) versus additive synthesis (building sounds from series of partials), noting additive/FFT resynthesis is beyond this project’s scope.[youtube]​

Voices and algorithm design

• A “voice” is defined as everything triggered by a note event; in typical synths this means oscillators, envelopes, VCA, and filter, and multiple voices give polyphony.[youtube]​

• His system uses two analog and three digital voices: analog voices carry melodic lines, while digital voices provide auxiliary harmonies tied to the analog behavior.[youtube]​

• Two simultaneous melodies are created by filling arrays with random values quantized to notes; values are gradually replaced over time, creating evolving melody and harmony without a fixed metronome, emphasizing temporal fluidity.[youtube]​

Hardware and hybrid analog–digital details

• The analog section uses two CEM3340‑type oscillator ICs, a 3360 VCA, and a 3320 low‑pass filter, with one shared filter for both analog voices to save parts.[youtube]​

• A 12‑bit MCP4822 DAC outputs control voltages for pitch, envelopes, cutoff, and resonance, while the Daisy Seed microcontroller’s onboard DACs provide PWM to drive analog square waves.[youtube]​

• He adopts a 480 mV per octave standard (instead of 1 V/octave) to fit within the DAC’s ~4 V range, then stores scales as linear millivolt values (e.g., semitone 40, whole tone 80, minor third 120 … octave 480) in arrays.[youtube]​

• Digital oscillators use the same scale arrays but convert the linear values to exponential frequency in code, while analog oscillators rely on their internal lin‑to‑exp converters.[youtube]​

Signal flow and finishing

• The combined analog signal is attenuated, digitized by the microcontroller, processed with overdrive and a stereo “wobbly” delay (also compensating for the single‑oscillator voices), then sent to the amplifier and stereo outputs.[youtube]​

• Visually, the sculpture is built with clean, open‑air, “3D” soldering, emphasizing its role as both circuitry and physical artwork.[youtube]​

• The video ends with a showcase of the completed piece sounding and a brief invitation to his Patreon for code and schematics.[youtube]​