# Decision Record ## Decisions - Treat the pianola as a pneumatic player-piano mechanism coupled to an existing or representative piano action. - Uplift readiness to `L2 V5 build-packet candidate` for review and prototype planning only. - Keep all dimensions, roll scales, tracker-bar coordinates, vacuum pressure, action travel, tuning data, CAD, and DXF work out of the packet. - Make the first physical work a single-note pneumatic chain before any full tracker bar or keyboard-width assembly. - Keep expression, sustain, and tempo-control branches separate from the first note-actuation proof. - Add `cut-list.csv` as a coupon and fixture planning register, not as a cut geometry release. - Keep all artifact authority at `concept_only` or `pending_measurement`. ## Assumptions - A perforated roll passes over a tracker bar. - Tracker-bar pressure changes operate pouches and valves. - Pneumatic output actuates a piano action rather than directly sounding a separate instrument. - Timing, leakage, reset, and serviceability are the main early risks. - L2 can name coupons, fixtures, logs, and sequencing, but cannot promote any physical parameter to fabrication authority. ## Open Questions - Which measured roll/tracker-bar standard or historical player-piano family should govern the first L2 parameter set? - Should the first rig use suction, pressure, or a hybrid representation of the pneumatic chain? - What pouch and valve materials can be tested without overclaiming durability? - How should expression and sustain coding be introduced after single-note response is measured? - What representative piano action is safe to use for actuation tests? - What is the safest way to intentionally add controlled leaks for diagnosis? - What service interval should be simulated before choosing permanent casework? - Which measurements belong in a future validation table before any L3 claim? ## L2 Prototype Gates - Select a measured reference frame without copying unreviewed dimensions into this packet. - Build or source one paper-strip coupon and one tracker-bar sensing coupon. - Bench one pouch/valve pair and log leak behavior, response, reset, and missed triggers. - Couple one pneumatic actuator to a representative piano action or safe action load. - Record serviceability observations for tracker cleaning, pouch replacement, valve adjustment, tubing inspection, and paper handling. - Review whether expression, tempo, sustain, or reroll controls can be added without hiding the single-note failure modes. ## Not Accepted As Evidence Yet - Prose descriptions of historic pianola dimensions. - Any unmeasured roll scale, tracker-bar layout, vacuum level, or linkage geometry. - CAD, DXF, renders, or photos that do not cite measured or reviewed authority. - Piano tuning or acoustic claims unrelated to pneumatic actuation.