reasampler/TODO-1.0.md

TODO-1.0

Post-1.0 enhancement queue for the ReaSampler 9000 instrument. Three items, in Daniel's ordering (2026-07-28). Deliberately specified at the level of product intent, user-visible behavior, and acceptance criteria — no implementation design, no file/module references. These were authored while Phase Q was restructuring the tree; the implementing engineer maps each spec onto the post-Q layout at execution time. Each item preserves Daniel's raw ask verbatim as the source of truth, then breaks it into behavior, open questions, and an observable acceptance gate.

A follow-up answer round from Daniel (2026-07-28) settled most of the open questions. Each item now carries his follow-up verbatim alongside the original ask; settled answers are folded into Behavior (marked settled by follow-up), and only the genuinely unresolved remainder stays under Open questions.

Ordering note: item 1's curve/overlay treatment explicitly anticipates item 2's filter envelope ("filter to be added"), and item 3 layers on both. They can land in sequence or together, but 1 and 2 are prerequisites for 3's full surface.

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1 — Envelope editor: per-deck radio switch, segment curve dials, overlay recolor

Daniel's ask (verbatim, 2026-07-28).

The VST envelope editor visual is a great start but we need to add some features. The Amp AHDSR is currently always displayed. We need to add a radio switch to the corner of each env knob deck which makes THAT envelope editable via the graphic waveform overlay. This is currently the amp and pitch envelopes, with filter to be added (see below). All envelopes (amp AHDSR, Pitch AD, Filter AHDSR) should be enhanced to have editable segment curve values. This should be an exponential function with the exponent scalar parameter for each sloped segment having possible values from 0.1 to 10. The knob deck radial knobs for the sloped curvable segments will have an INNER dial, with its own inner arc, hover accent (tertiary purple), needle, and numerical label which controls the curve for that sloped segment. Also the graphical envelope editor draws its segments in secondary blue, which contrasts poorly against the primary green waveform display. Change those to tertiary purple.

Daniel's follow-up (verbatim, 2026-07-28).

yes, one overlay (or none). Everything besides Hold and Sustain, right? "is 1.0 the linear neutral" CLAUDE, y=x^1.0 is linear!! of course! yes dragging on the segment (add a round knot midsegment) adjusts the curve.

Intent. Grow the envelope-overlay editor from an amp-only fixture into the shared graphical surface for every envelope in the instrument, and give every envelope shapeable (non-linear) segments — while fixing the blue-on-green contrast failure.

Behavior.

• Radio switch per envelope deck. Each envelope knob-deck group (currently AMP ENVELOPE and PITCH ENV; the filter envelope joins when item 2 lands) gains a radio switch in the corner of its deck. Selecting a deck's radio makes that envelope the one displayed and editable in the graphic waveform overlay — replacing today's behavior where the Amp AHDSR is always the displayed envelope. The switch is exclusive: one overlay-active envelope at a time, or none — no-envelope-shown is a valid state, not an error. (Settled by follow-up.)
• Segment curve values on all envelopes. Amp AHDSR, Pitch AD, and Filter AHDSR all gain an editable curve value per sloped segment. The curve is an exponential function; the per-segment parameter is the exponent scalar, range 0.1 to 10.
• Which segments are sloped. Every stage except Hold and Sustain — for an AHDSR that is Attack, Decay, and Release; for the Pitch AD, both stages. (Settled by follow-up.)
• Linear neutral. Exponent 1.0 is the linear neutral (y = x^1.0 is linear). (Settled by follow-up — emphatically.)
• Curve editing in the overlay. Dragging on a segment in the overlay adds a round mid-segment knot whose drag adjusts that segment's curve — the overlay is a curve-edit surface in its own right, alongside (not instead of) the inner dial. (Settled by follow-up.)
• Inner dial on curvable-segment knobs. Every knob-deck radial knob that controls a sloped, curvable segment gains an inner dial: its own inner arc, its own hover accent (tertiary purple), its own needle, and its own numerical label. The inner dial controls the curve exponent for that segment; the outer knob keeps controlling the segment's time/level value as today.
• Overlay recolor. The graphical envelope editor's segments change from secondary blue to tertiary purple (secondary blue contrasts poorly against the primary green waveform behind it).

Open questions.

• Default overlay selection on open. Exclusivity and the none-state are settled; what is the default when the editor opens — the Amp AHDSR (today's behavior) or none?
• Pre-existing instances. Should saved instances from before this change load with every curve at the linear equivalent (exponent 1.0) so their sound is unchanged? (The neutral point itself is settled; this is only the load-behavior half. The product requirement is "old instances sound identical.")

Acceptance criteria.

• Each envelope deck shows a corner radio switch; activating one puts that envelope in the overlay, editable there, and the overlay tracks the switch immediately. At most one envelope is overlay-active; with none active, the overlay draws no envelope.
• Every curvable-segment knob shows the inner dial (inner arc, tertiary-purple hover accent, needle, numeric label); sweeping it through 0.1 → 10 visibly reshapes the overlay segment and audibly reshapes the envelope on played notes. Hold and Sustain knobs carry no inner dial.
• Dragging on an overlay segment adds a round mid-segment knot; dragging the knot adjusts that segment's curve, and the segment's inner dial reflects the same value.
• Overlay envelope segments render in tertiary purple and are clearly legible against the primary green waveform.
• A project saved before this change reopens with unchanged audible envelope behavior.

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2 — MM preamp Filter: resonant HP/LP stage in the voice pipeline

Daniel's ask (verbatim, 2026-07-28).

MM preamp Filter: We must implement a new processing point in the sampler audio pipeline, after pitch env, before amp, for filtering. The processor for this will be based on code I wrote for the cortex M4 for resonant high and lowpass filtering. The filter will have parameters for mode, cutoff, Q, and mod amt, then the AHDSR controls as described above. The knob deck row will then be relaid out in signal flow order: pitch -> filter -> amp

Daniel's follow-up (verbatim, 2026-07-28).

modes beyond the pass filters will be added later. cutoff range full audio spectrum, log scaled, fully open to fully closed, Q should go from 0.1 to 10 again, scaled around root 2 at the center. mod amt targets cutoff, -100% - +100% to cover full range from either end. per-voice. label it "Filter"

Intent. Add the instrument's first filter stage — resonant high-pass and low-pass — as a new fixed point in the per-voice signal path, with its own AHDSR envelope, and make the knob-deck row read in signal-flow order.

Behavior.

• Pipeline position. A new processing point in the sampler audio pipeline: after the pitch envelope, before the amp stage.
• DSP source. The filter processor is based on Daniel's own Cortex-M4 resonant high/lowpass filter code. That code is an input Daniel supplies at implementation time — it is not in this repo and this spec does not characterize it beyond "resonant high and lowpass."
• Parameters. Mode, cutoff, Q, and mod amt — then the AHDSR controls, treated exactly as item 1 specifies (curvable sloped segments with inner dials, overlay editability via the filter deck's radio switch). (Ranges settled by follow-up:)
  • Mode: high-pass and low-pass now; modes beyond the pass filters are explicitly deferred to later.
  • Cutoff: the full audio spectrum, log scaled, from fully open to fully closed.
  • Q: 0.1 to 10 (the curve-exponent range again), scaled so √2 sits at the center of the control.
  • Mod amt: bipolar, −100% to +100%, targeting cutoff — covering the full range from either end.
• Per-voice. The filter processes per voice — each sounding voice runs its own filter with its own envelope state. (Settled by follow-up.)
• Label. The user-facing deck-group label is "Filter". "MM preamp" is working shorthand for the DSP lineage, not UI text. (Settled by follow-up.)
• Deck reorder. The knob deck row is relaid out in signal-flow order: pitch → filter → amp.

Open questions.

• Other mod sources. Mod amt targeting cutoff is settled; whether any other mod sources (velocity, key-tracking) are in scope now or deferred is unstated.
• Parameter storage: per-zone or per-instance. Per-voice processing is settled, but it is compatible with either storage side. Existing playback parameters live per-zone with Sample/Zone panel parity; VOICE and MASTER are per-instance exceptions. Which side do the filter parameters fall on?
• Neutral default. Should the filter default to a bypass/neutral state so pre-existing saved instances (and freshly loaded captures) sound unchanged until the user engages it?

Acceptance criteria.

• With the filter engaged, played notes are audibly filtered at the specified pipeline point: the filter acts on pitched (post-pitch-envelope) signal, and the amp envelope still shapes the filtered result (audible ordering: pitch → filter → amp).
• Mode, cutoff, Q, and mod-amt controls appear in a deck group labeled "Filter"; the filter AHDSR gets the full item-1 treatment (curve inner dials, corner radio switch, tertiary-purple overlay editing).
• Cutoff sweeps the full audio spectrum on a log scale, from fully open to fully closed; Q spans 0.1 → 10 with √2 at the control's center; mod amt at −100% and at +100% each drive cutoff across the full range, from opposite ends.
• High Q audibly emphasizes the cutoff region (resonance) in both HP and LP modes.
• Two simultaneously sounding voices at different envelope phases are filtered independently (per-voice processing is audible, not a shared instance-wide filter).
• The deck row reads pitch → filter → amp left-to-right.
• A project saved before this change reopens sounding identical (pending the neutral-default confirmation above).

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3 — Alternative Spline EGs: hard/smooth multi-segment monotonic splines

Daniel's ask (verbatim, 2026-07-28).

Alternative Spline EGs: Every processor which has an envelope will have the ability to change the Staged EG to a Spline EG, based on the monotonic splines for the velocity curve. HOWEVER, we will need to enhance the (singly implemented, multi referenced) spline algorithm to support multiple segments that DON'T minimally smooth the spline, so that hard points are possible. In other words, the contour of the EG will be defined by 1 or more monotonic spline functions which together form the full time function for that processor, such that the first three points could make a curved segment, which connects at a sharp angle to the next three points, finishing out the contour over the full sample length. Control-clicking a point makes it a "hard" or "smooth" point (toggled, smooth by default) which when hard does no curve smoothing on either side segment, forming the natural sharp angle instead of a continuous derivative. This enhanced spline drawing will be used for the velocity-amp transfer curve as well as the pitch, filter, and amp EGs (if they are in spline mode).

Daniel's follow-up (verbatim, 2026-07-28).

dual state, save but inactive. Default Curve Spline is a smooth y=1-x. Gate mode is not available when the Spline is used, spline always covers the full sample length. The spline curves don't have to rise AND fall, they also aren't globally monotone, the default curve is a smooth downward slope over the length. all the soft points between any hard points will be smooth/monotone.

Intent. Offer a free-drawn alternative to every staged envelope: the user switches any EG from Staged to Spline mode and draws the contour directly, with the monotonic-spline machinery already proven by the velocity curve — enhanced so sharp corners are possible, not everything smoothed.

Behavior.

• Mode toggle per EG. Every processor that has an envelope (pitch, filter, amp) can switch its Staged EG to a Spline EG.
• Dual state — save but inactive. Both the Staged and the Spline state are persisted; switching modes keeps the inactive one saved but inactive. No conversion, no discard — round-tripping Staged↔Spline restores the other mode's shape untouched. (Settled by follow-up.)
• Gate unavailable in Spline mode. Gate mode is not available while a Spline EG is active; the spline always covers the full sample length — a pure time function over the sample, i.e. the Trigger/one-shot playback model. (Settled by follow-up.)
• Not globally monotone. Spline contours don't have to rise and fall and are not globally monotone; the monotone guarantee is per-segment — all soft points between any hard points are smooth/monotone (no overshoot between adjacent points). (Settled by follow-up.)
• Default contour. A new Spline EG defaults to a smooth y = 1 − x — a smooth downward slope over the full sample length. (Read as the Spline-EG default contour; not a change to the velocity→amp transfer curve's existing default.) (Settled by follow-up.)
• Spline foundation. The Spline EG is based on the monotonic splines used for the velocity curve. The spline algorithm is singly implemented and multi-referenced; the enhancement below applies to that one implementation and flows to every consumer.
• Hard points. The algorithm is enhanced to support multiple segments that don't minimally smooth the spline, so hard points are possible: the EG contour is defined by one or more monotonic spline functions which together form the full time function for that processor — e.g. the first three points form a curved segment that connects at a sharp angle to the next three points, finishing the contour over the full sample length.
• Hard/smooth gesture. Control-clicking a point toggles it hard/smooth (smooth by default). A hard point does no curve smoothing on either adjacent segment — the natural sharp angle stands instead of a continuous derivative.
• Shared across consumers. The enhanced spline drawing serves the velocity→amp transfer curve as well as the pitch, filter, and amp EGs (when those are in spline mode). The velocity curve gains hard-point support by the same enhancement.

Open questions.

• Time-axis storage. Full-sample coverage is settled ("spline always covers the full sample length"); what remains is only whether the stored contour is normalized to the sample length (so it rescales when a different-length capture loads) or anchored some other way.
• Point-editing grammar. Point add/delete gestures and any point-count bound are unstated. The velocity-curve popup already established right-click node delete — reuse of that grammar seems natural but is Daniel's call.
• Staged controls while Spline is active. Sound-wise the staged EG is inactive in Spline mode (settled by dual-state). Still open at the UI level: do the staged segment knobs/inner dials stay editable (editing the dormant staged state) or go inert/greyed until the user switches back?

Acceptance criteria.

• Each of the pitch, filter, and amp EGs offers a Staged/Spline mode switch; in Spline mode the overlay (via the item-1 radio switch) shows and edits the drawn contour, and played notes audibly follow it.
• Control-click toggles any point hard/smooth; points are smooth by default; a hard point renders a visible sharp angle with no smoothing on either adjacent segment, and the discontinuous slope is audible where the modulation target makes it so (e.g. a pitch EG corner).
• A contour of several segments joined at hard points plays back over the full sample length exactly as drawn — including contours that rise and fall freely (no globally-monotone restriction), with no overshoot between any adjacent pair of points.
• A freshly created Spline EG shows the smooth y = 1 − x default contour.
• While a Spline EG is active, Gate mode is not selectable; the spline plays as a pure time function over the full sample length.
• Staged↔Spline round-trip preserves both states: switch to Spline, draw, switch back — the staged values are exactly as left; switch forward again — the spline contour is exactly as drawn. Both survive save/reload.
• The velocity→amp transfer-curve editor supports the same control-click hard/smooth toggle with identical rendering behavior.