# Decision Record ## Decisions - Treat the waterphone as an idiophone design study, not a fabrication-ready plan. - Center the concept on a metal resonator bowl, central neck, tuned rim rods, internal water pitch-bend behavior, and bowed/struck playing gestures. - Uplift to L2 by naming subsystems, candidate part classes, and evidence gates for future measurement. - Keep every artifact at `concept_only` or `pending_measurement` authority. - Avoid exact dimensions, DXF coordinates, rod counts, rod pitches, fill volumes, acoustic values, or tuning claims until measured evidence exists. - Use coupon tests for rods and attachments before designing a full rim field. ## Open Questions - Which bowl material and forming method gives the best bow/strike response without corrosion or handling noise? - Should the neck be a pure handle, a fill/service port, or both? - Which rod attachment method balances sustain, repairability, and reliable energy transfer? - How should water fill level be marked and repeated between sessions? - Which measurements are required before any rod ordering can be called a tuning map? - Which joint method gives a useful bowed response while staying repairable? - How should leak, corrosion, cleanup, and storage be validated before a wet prototype is handled by a player? - Does the neck need to be removable for service, or should it remain a sealed handle with a separate fill path? ## Promotion Gates - L2 records subsystem intent, candidate part classes, and pending measurement gates only; it does not authorize fabrication. - Move beyond L2 only after measured dry-bowl response, rod coupon tests, attachment trials, water-fill response logs, and leak/safety checks exist. - Promote CAD/DXF authority only from reviewed measured templates or reviewed parametric CAD, not from concept text or generated visuals.