# Decision Record ## Decisions - Treat the Marxophone as a fretless zither plus spring-hammer action study, not a fabrication-ready plan. - Promote readiness to `L2 V5 build-packet candidate` for review and prototype planning only. - Center the concept on string courses, a resonant zither body, spring-mounted hammer arms, player-actuated keys or levers, and tremolo from rebound dynamics. - Keep every artifact at `concept_only` or `pending_measurement` authority. - Avoid exact dimensions, string gauges, course counts, pitch targets, spring rates, hammer masses, key travel, DXF coordinates, or acoustic values until measured evidence exists. - Begin with a one-course action coupon before planning a full instrument. - Add `cut-list.csv` as a coupon/module planning surface only; it does not authorize cutting stock or making action parts. ## Open Questions - Which string material and tension range supports a clear repeated hammer attack without excessive wear? - Which hammer tip material creates tremolo without harsh mechanism noise? - Should the action use keys, tabs, levers, or another player interface? - Which spring and pivot arrangement gives rebound without double-trigger chaos or sluggish return? - How should useful tremolo density be measured before a tuning map exists? - Which tests separate string-bed behavior from hammer-action behavior? - What safety controls are required before spring and tensioned-string trials? ## Promotion Gates - Move beyond L2 only after measured string response, hammer coupon data, spring rebound logs, action noise checks, and player-control trials exist. - Promote CAD/DXF authority only from reviewed measured templates or reviewed parametric CAD, not from concept text or generated visuals.