memlnaut-nisps/docs/slp-workshop/SPEC.md

SLP-Workshop — output modes, gate sequences & config UX

Status: DRAFT / spec-only (2026-06-28). The SLP-Workshop firmware exists as the slp_workshop mode (Synth Library Portland workshop; reuses the MEMLCelium engine + MLP shape verbatim, foregrounds the Jolt / OU-noise learning gestures — branch workshop/synth-fw-audit). The three output modes below are a planned evolution: compile-time slices of that mode. This document specs the mode model, the Manifold-side gate-sequence configuration, and a proposed UI so the firmware and the browser app stay aligned. The output-mode slicing + Manifold config are NOT implemented yet.

Companion docs: docs/useq-celium/protocol.md (the CV wire protocol), the manifold backends (manifold/src/backends/), the input layer (manifold/src/inputs/).

Decisions locked (2026-06-28, operator): (1) hardware keeps exactly 2 ratio sequences (memlcelium verbatim); the browser may instantiate as many as the user wants. (2) The 3 uSEQ gate-only jacks make gates optional — pure CV is valid; if doing gates at all, use those 3 first, then convert CV jacks. (3) Split-net input is per-input-channel engine routing (each pad/stick/CC tagged Continuous or Rhythm). (4) Internal BPM clock now; external-MIDI-clock sync is a later nicety.

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1. Ground truth: what memlcelium actually is

memlcelium is the hybrid, and it is one MLP, not two:

• Net: MLP<4, [10,14,18], 56> (nisps/engines/memlcelium.hpp).
• The 56 outputs are split:
  • [0..13] — sequencer: 2 sequences × 7 ratio-seq params each.
  • [14..55] — synthesis: 42 continuous params (Voice 0 + Voice 1).
• The single net therefore produces both the continuous values and the RatioSeq parameters. An internal RatioSeq tick turns the seq params into note triggers; the engine already exposes pop_events() so those triggers can be consumed externally (MIDI / CV / gate) — that is the hook for gate outputs.

So the two-separate-networks hybrid is a genuinely different topology (two MLP heads), which is why the hardware does the shared-net version and only the browser (more compute, dynamic) does the split one.

7 ratio-seq params per track

ratios[0..2] (3), phasor_mul (1), phase_off (1), amp_ratios[0..1] (2) = 7. (The April browser uSEQ-Celium used 8 — it added a pulse-width param. Use 7 for firmware parity; pulse width can be an optional 8th later.)

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2. The unifying model: two output STREAMS

Everything below collapses to two output streams, each driven by an MLP head:

Stream	MLP outputs	Generates	Routes to
Continuous	1 value per channel	smooth 0..1 values	MIDI CC / CV jack
Rhythm	7 params per gate-sequence track	clock-driven gates	MIDI note / gate jack

A mode is just which streams are active and whether they share a network.

How the Rhythm stream generates gates (RatioSeq)

Per gate-sequence track, each control tick (nisps/engines/* ratio_seq_*):

1. A shared internal-BPM clock advances a bar phasor. (External-MIDI-clock sync is a desirable later addition, not a launch requirement — operator.)
2. seq_phasor = (bar_phasor × phasor_mul + phase_off) mod 1.
3. ratio_seq_3(seq_phasor, ratios, pw=0.5) → boolean gate (the 3 ratios carve the cycle into proportional segments; the phasor's segment + pulse-width decide high/low).
4. ratio_seq_2(amp_ratios) → 2-level velocity (127 / 64).
5. Rising edge → note-on / gate-high (with velocity); falling edge → note-off / gate-low.

So a gate is clock + learned pattern, not a threshold on a continuous value — this is what makes "Rhythm" a distinct stream, and why it needs its own 7-params per track rather than one output per gate.

Defaults = firmware parity (pulse width fixed at 0.5; 2-level velocity). Two deferred extensions, not blocking: a per-track pulse-width (the 8th param → controllable gate length, matters for envelope vs trigger) and continuous velocity/accent instead of the 127/64 two-level. Add later if the workshop wants them.

Where RatioSeq runs in the browser: when the active engine is the memlcelium / SLP WASM engine, consume pop_events(). For CV/MIDI modes that don't run that audio engine, a small TS RatioSeq fed by the Rhythm MLP's 7-params/track drives the gates. (Implementation note — not built yet.)

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3. Modes

Firmware (SLP-Workshop) — compile-time, one chosen at build

Always exactly 2 ratio sequences (memlcelium verbatim) — the firmware does not vary sequence count.

Mode	Streams	Net	MLP output_size
Continuous only	Continuous	1	continuous params only
Continuous & Rhythm (= memlcelium)	both, shared	1	14 seq + 42 synth = 56
Rhythm only	Rhythm	1	2 × 7 = 14 seq params

Browser (Manifold) — dynamic, switchable live

Same three plus a fourth, and with as many ratio sequences as the user wants (each gate sequence = its own independent 7-param track; the net reshapes to suit):

• Continuous & Rhythm (split nets) — Continuous MLP + a separate Rhythm MLP. Browser-only (two MLP heads; hardware uses one). output_size: shared net = continuous + 7 × n_gates (mind the 126-output WASM cap → ~16 gates max shared); split net = the Rhythm net is sized independently, so it scales further.

The browser mode is implied by the Outputs config (§4), not a separate picker: choosing continuous-count > 0 and gate-sequences = 0 ⇒ Continuous-only; gates > 0 with Shared net ⇒ hybrid-shared; gates > 0 with Separate net ⇒ hybrid-split; continuous-count = 0 ⇒ Rhythm-only.

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4. Configuring gate sequences (Manifold, CV and MIDI modes)

The user can add gate-sequence outputs in both CV and MIDI modes. Two new controls only; everything else is automatic.

4.1 The two output kinds

• Continuous → CC (MIDI) / CV jack (CV).
• Gate sequence → note (MIDI) / gate jack (CV). Each = one RatioSeq track.

MIDI mode — two independent steppers (capped by the model output budget):

Continuous (CC):   [ 8 ]
Gate sequences:    [ 2 ]      each → a rhythm track → note on/off

CV mode — hardware is fixed (11 PWM/CV-capable + 3 digital/gate-only), so the two counts are linked. Gates are optional — pure CV (0 gates) is valid. One control:

uSEQ jacks            CV 11 · Gate 0
Gate sequences  0 ●───────────── 14
                └ first 3 are FREE (the gate-only digital jacks); the 4th+ convert a CV jack

Rule: gates ∈ [0, 14]; CV = gates ≤ 3 ? 11 : 14 − gates. So the first 3 gate sequences land on the dedicated gate-only jacks and cost no CV (gates 0→11 CV; 3→11 CV; 6→8 CV; 14→0 CV). "Add more gates by swapping CV outs to gate outs" only kicks in past 3. (If you want gates at all, those 3 gate-only jacks are there to use; if you don't, they sit idle and you keep all 11 CV.)

Wire-protocol impact: none. A CV jack acting as a gate just carries 0/full (or the 2-level velocity) in its u16 slot; the 3 dedicated gate bits stay the digital pins (docs/useq-celium/protocol.md). The CV backend's CvSpec already lets any output target a CV or a gate channel — this extends it so PWM jacks can be gate targets too.

4.2 The Rhythm network (shown only when gate sequences > 0)

Rhythm network:   ( Shared )   ( Separate ◀ default )

• Separate (default): the Rhythm stream gets its own MLP, so each input channel is routed to one of the two engines (Continuous or Rhythm). The routing is automatic per source kind:
  • XY pad (internal) → a second on-screen XY pad appears; pad 1 → Continuous, pad 2 → Rhythm.
  • Gamepad → double-stick: left stick → Continuous, right stick → Rhythm.
  • MIDI controller → per-CC routing: each learned CC has a small Continuous | Rhythm toggle, so the user assigns which knobs drive which engine. (The pad/gamepad cases are just the pre-grouped 2-axis versions of this same per-channel routing.)
• Shared: one MLP drives both streams; all input channels feed the single net (one pad / one stick / all CCs). This is the hardware-parity hybrid.

That is the whole decision surface: two numbers + one toggle. The second pad / double-stick / per-CC tag is a consequence of Separate, surfaced inline, not a separate mode control. It reuses the existing input layer (InputSource.axisCount() already supports gamepad single↔double-stick; per-axis labels exist via axisLabels()) — "Separate" adds an engine tag per input axis and composes a second xy-pad source / flips the gamepad to 4-axis as needed.

4.3 Per-output detail (advanced, optional)

In BackendAdvanced (full-depth modal), each output row can override the defaults: which model output drives each CC/CV; which rhythm track drives each note/gate; gate threshold (for continuous-derived gates); MIDI note#/channel; CV polarity. Defaults (identity assignment) make this unnecessary for the common case.

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5. Proposed UI summary (the "simple" target)

Outputs panel, top to bottom:

1. Output kinds — Continuous [n] + Gate sequences [n] (MIDI), or the linked Gate sequences 0–14 slider with the live CV n · Gate n readout (CV).
2. Rhythm network toggle ( Shared | Separate ) + the inline input surface (2nd pad / double-stick / per-CC engine tags) — only when gate sequences > 0.
3. The existing per-output rows (off/fixed/live, mute, arm, min/max/curve) + the per-backend specifics (CC#, CV jack, note#) as today.

No mode dropdown for the rhythm/continuous split — the counts + toggle are the mode.

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6. Open questions / deltas to build later

Build deltas (when we proceed):

• Manifold engine: today one MLP head on the spine. "Separate" needs a second Rhythm MLP head + per-input-axis engine routing. Scope: engine + input-layer.
• TS RatioSeq: a browser-side RatioSeq (or a pop_events() bridge) to turn Rhythm-MLP params into gate/note events for the CV & MIDI backends. 2 sequences on firmware; arbitrary count in the browser.
• MIDI backend: gate sequences → note on/off (it currently only sends CC).
• CvSpec: allow PWM jacks (cv1..cv11) to be gate targets (incl. velocity-CV), with the 3 digital pins as the first-used gate jacks.
• Reshape: shared-net output_size = continuous + 7 × gate_sequences (≤126 WASM cap) — confirm against the reshape/reset-on-reshape flow.
• Firmware output_size for "Continuous only" / "Rhythm only" — slices of the slp_workshop mode (workshop/synth-fw-audit); the firmware agent's call. This doc fixes the shapes, not exact counts.

Deferred niceties (explicitly not blocking): external-MIDI-clock sync; per-track pulse-width (gate length); continuous velocity/accent beyond 127/64.