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An FM synthesizer. 6 operators. 3 parallel stacks. 16 voices.
Built to approximate two things that don't exist inside it: a hurdy-gurdy wheel and a human mouth.
KVR thread: kvraudio.com/forum/viewtopic.php?t=629750
Testing notes and findings for the Kaiku VST3i pre-release evaluation.
The evaluation framework lives at rebraining.org/practice/music/kaiku — full exercise index with score PDFs, MIDI downloads, and instructions. This wiki records what was actually heard.
- Testing Protocol — REAPER setup, tempo, gain staging, render settings, what to listen for
- Exercises — E01–E17: what each exercise tests and what to expect
- Findings — session-by-session results, one entry per exercise
- Phase 2 Criteria — what Phase 1 results unlock or block
Three FM stacks in parallel (Tyhjyydenkaiku topology):
| Stack | Role | Ratio |
|---|---|---|
| A | F1 formant body | ~1.0× |
| B | F2 nasal partial | ~2.0× |
| C | Wheel carrier | 1.008× |
Stack C at 1.008× creates a slow beat against the fundamental — the wheel imperfection. At F#1 the beat period is ~2.7 seconds. At F#5 it reads as fast vibrato (~5.9 Hz). This is the instrument. Do not report it as a defect.
The Hiljaisuus LFO runs at 0.15 Hz — one full cycle every 6.67 seconds. Slow-tempo exercises (♩=40) are slow to let the LFO complete a visible cycle.
| Patch | Character |
|---|---|
| Tyhjyydenkaiku | The wheel beating — slow amplitude modulation from Cw at 1.008×. Present on every note across the full range. This is the instrument. |
| Kuilunsikiö | Visceral, before-it-becomes-sound quality. Rougher than Tyhjyydenkaiku. |
| Pohjankaiku | Mellotron weight. Slower attack character. The echo across the north. |
| Kuilukaiku | Stripped. The wheel alone. No formant body. Sparse. |
A consistent +1–4¢ sharp offset is present across all patches and voices. This is stable — the Cw wheel stack at 1.008× interacting with the tuning reference. It is not a defect. Flag any pitch that drifts within a sustained note, or any note that misses its scale degree.