# Decision Record ## Decisions - Treat the nyckelharpa as a keyed bowed fiddle, with tangent action as the primary engineering risk. - Keep all dimensions, tuning, string gauges, bridge geometry, tangent layout, and CAD/DXF work out of the packet. - Model the first prototype as separate test rigs before a full instrument: one bowed-string/tangent contact rig, one keybox travel rig, and one sympathetic-string clearance/resonance rig. - Prefer serviceable tangent adjustment over hidden precision in the first physical study. - Uplift to L2 by adding shop-planning surfaces, not by promoting any measured or fabrication authority. - Add `cut-list.csv` as a planning ledger for blanks and mockups only; it must not be read as a cut-ready part list. - Keep the keybox removable until tangent contact, sympathetic-string clearance, and service access have been reviewed together. ## Assumptions - Melody strings are bowed directly. - Wooden tangents stop the melody strings when keys are pressed. - Sympathetic strings are routed below or through the keybox and are not stopped by the main tangent action. - Key travel, tangent face, bridge, body, and sympathetic path must be adjusted together after real measurements. - The first useful shop artifact is a bench rig, not a complete decorated body. - A future measured reference tradition or instrument family will be selected before any final layout, tuning, or stringing schedule. - Sympathetic resonance may require damping or isolation experiments; a weak or noisy response is not a failure if it is logged honestly. ## L2 Shop-Planning Choices - Use modular assemblies: one-string rail, keybox cassette, tangent carrier, sympathetic underpass, and body planning shell. - Favor reversible fasteners and removable panels in test rigs. - Require failure-mode logging before changing multiple variables at once. - Keep all part quantities as `estimate_pending_measurement`. - Keep the visual authority register conservative: concept and pending measurement only. ## Open Questions - What reference nyckelharpa family or style should govern the first measured packet? - How many melody, drone, and sympathetic strings should be studied after a reference frame is chosen? - Should the first keybox use sliding wooden keys, hybrid low-friction guides, or a removable experimental cassette? - What tangent adjustment method gives enough setup control without making the action fragile? - How should sympathetic strings be protected while preserving tuning access? - What guide material and return approach keep keys quiet without excessive friction? - Where should the keybox open for cleaning, tangent replacement, and sympathetic-string service? - What body/soundboard mockup is sufficient to test load paths without pretending to be the final resonator? ## Next Work - Select a reference tradition or measured instrument source. - Build a one-key tangent test rig before designing a full keyboard. - Build a sympathetic-string clearance mockup under an open keybox. - Record measured key travel, tangent contact behavior, buzzing, return noise, bow clearance, and sympathetic response before any authority upgrade. - Populate a future validation table with measured results from the one-key rig. - Update the cut list only after measured reference dimensions or reviewed CAD exist. - Add photos or diagrams only as concept/support visuals unless a reviewed dimensional source is also registered.