Maddie MOD2
Spirals
Oscillator · Experimental
Auditory illusions and impossible sounds — Shepard tones, Risset rhythms, and tritone paradoxes.
- Width
- 4 HP
- Depth
- 28 mm
- Power
- +12V / −12V / +5V
- MCU
- Seeed XIAO RP2350
- Controls
- 3 pots · button · LED
- I/O
- 1 CV in · PWM audio out
Overview
Spiral 4Ever is a generator of auditory illusions and impossible sounds — the sonic equivalent of an endless staircase. Across nine modes it produces Shepard tones that rise or fall forever, Risset rhythms that accelerate endlessly, and tritone paradoxes that play with pitch ambiguity.
Modes
| # | Mode | |
|---|---|---|
| 0 | Shepard Rising | Infinitely ascending tone |
| 1 | Shepard Falling | Infinitely descending tone |
| 2 | Barber Pole | Stripe envelope + AM |
| 3 | Risset Rhythm | Infinitely accelerating beats |
| 4 | Tritone Paradox | Ambiguous interval |
| 5 | Tritone Explorer | Pitch-class experiment |
| 6 | Shepard Cluster Maj | Rising/falling major triad |
| 7 | Shepard Cluster Min | Rising/falling minor triad |
| 8 | Euler Spiral | Circular pitch with spectral rotation |
Panel & I/O
| Control | Pin | Function |
|---|---|---|
| POT1 | A0 | Center frequency (V/Oct CV) |
| POT2 | A1 | Sweep speed |
| POT3 | A2 | Envelope width / pitch class / spiral spread |
| BUTTON | GPIO6 | Short = cycle modes · long = toggle direction |
| OUT | GPIO1 | Out — PWM audio |
| LED | GPIO5 | Solid = direction up |
Features
- Nine psychoacoustic illusion modes
- Endless Shepard tones and Risset rhythms
- Tritone-paradox experiments
- Sweepable speed and direction
© 2026 Maddie Synths · firmware based on work by the HAGIWO MOD2 community · original firmware CC0 1.0 · hardware design by Hagiwo