diff --git a/docs/agents/LEDGER.md b/docs/agents/LEDGER.md
index a243e6a..ff9dc9d 100644
--- a/docs/agents/LEDGER.md
+++ b/docs/agents/LEDGER.md
@@ -65,7 +65,7 @@ Standing principles (memory): scroll > click; nothing duplicated; one global ins
 3. **Piano: 2×2 smaller keyboards** — "smaller keyboards so there would be 2×2 for each chord." The 4 pianoVoicing styles in a 2-col × 2-row grid of compact MiniPianos per chord.
 4. **Remove play buttons** — "leave off the PLAY buttons, they take up a lot of space for no reason, no need to hear it." Drop every ▶ from the voicings rail (and the licks strip — Maestro extension, matching the stated glance-over-audio preference; also removes the shared-sequencer blocker so piano licks can wire in cleanly).
 5. **Licks: uniform size + follow the instrument** — "the licks section should all have the same size and transform into piano when selected." Uniform card size; the strip follows the global GUITAR/PIANO/BASS selector — wiring the deferred PianoLickCard into the strip (bass → no licks / honest note).
-6. **Related progressions: same-style bridge/chorus/modifications** — "i would also want bridge/chorus/modifications in the same style… say i select jam roulette with blues, then i want for that progression other options and not necessarily go into other styles." Same-style variations for the active/rolled loop. **User decided 2026-07-13: reuse existing KB same-style progressions (lightest option) — NO computed modifications, NO new authored sections.** So: when a style is active (rolled or live-detected), RelatedProgressions surfaces the OTHER progressions of that style first, reframed as "variations / sections to try in this style"; cross-style stays available only when no style is locked.
+6. **Related progressions: same-style bridge/chorus/modifications** — "i would also want bridge/chorus/modifications in the same style… say i select jam roulette with blues, then i want for that progression other options and not necessarily go into other styles." Same-style variations for the active/rolled loop. **User decided 2026-07-13: reuse existing KB same-style progressions (lightest option) — NO computed modifications, NO new authored sections, NO song forms (verse/chorus/bridge — KB has no section data and most progressions are complete forms; Maestro + user agreed not to fake it).** So L-72 ships the honest same-style variations. **NEW feature added same day** (user: "imagine we play Am C F, i'd like an alternative to that F… an option that says 'try this'… i want musicians to learn how they can make the jam more interesting"): a **per-chord "Try this" chord-substitution** surface — for a loop chord in the detected key/style, suggest a small curated set of alternative chords (relative sub, borrowed-minor colour, extension colour, a circle-of-fifths / secondary-dominant move) each with a plain-language WHY. Circle-of-fifths-informed where it applies (honest that not all subs are circle-adjacent). Keep it simple/learnable, not a reharm engine. → tasks D-73/L-73/L-74 below.
 
 Standing principles (memory): scroll > click; nothing duplicated; one global instrument selector; playhead highlights; glance over audio. User is PRESENT — notification-driven, no cron. Weights: Muse 3, Luthier 3, Critic gate.
 
@@ -76,10 +76,13 @@ Standing principles (memory): scroll > click; nothing duplicated; one global ins
 | L-70 | Implement the voicings rail per D-70: guitar ≤4, 2×2 smaller piano, ▶ removed, dark hidden scrollbars | engineering | backlog | D-70 | `src/components/GlanceRail.jsx`, `src/components/VoicingBrowser.jsx`, `src/index.css` (scrollbar CSS) (+ per doc — re-lock at promotion) | rail matches the spec; no ▶; guitar ≤4; piano 2×2; scrollbars hidden+dark+functional; build + smoke green |
 | L-71 | Implement the licks strip per D-70: uniform card size, follow the global instrument (wire PianoLickCard), ▶ removed | engineering | backlog | D-70, L-70 | `src/components/JamGuide.jsx` (LicksStrip), `src/components/LickCard.jsx`, `src/components/PianoLickCard.jsx` (+ per doc — re-lock at promotion) | licks uniform; piano licks show under PIANO; no ▶; bass honest; build + smoke green |
 | D-72 | Same-style related-progressions design (user answer = reuse existing KB): decide the presentation — when a style is active, RelatedProgressions leads with same-style siblings reframed as "variations / sections to try in {style}" (labels/section framing that reads as bridge/chorus/variation without new content); how the active style is known (roulette seed carries it; live detection's match yields it — name the prop/source); whether cross-style entries stay as a secondary "other styles with these changes" section or are dropped when a style is locked; empty/edge states. Files disjoint from the rail/licks chain (RelatedProgressions.jsx only) → runs in PARALLEL | design | done | — | `docs/design/related-same-style.md` | presentation spec'd against the real RelatedProgressions/match.js; active-style source named; L-72 bounded |
-| L-72 | Implement D-72: RelatedProgressions leads with same-style variations when a style is active; reframed labels; cross-style demoted/dropped per the doc. **HELD (2026-07-13) pending user decisions:** (1) whether to add a "song forms" feature (verse/chorus/bridge — KB has NO section data today; Maestro recommended shipping honest variations now + a separate forms sprint if wanted); (2) gate finding-A — keep the secondary cross-style section when a style is locked (goal #6 says drop it) — user arbitrates; (3) fold gate finding-B — null the role phrase when a same-style sibling shares NO transitions with the loop, so no false "variation" claim | engineering | held | D-72 | `src/components/RelatedProgressions.jsx`, `scripts/smoke.mjs` (§8 re-pin) | same-style-first when locked; honest cross-style fallback; role phrase honest (finding-B); build + smoke green |
-| C-70 | Sprint-end sweep + PR #3 update | quality | backlog | L-70, L-71, L-72 | (none — verification) | all green; PR updated |
+| L-72 | Implement D-72: RelatedProgressions leads with same-style variations when a style is active; reframed labels; cross-style demoted/dropped per the doc. **Unblocked 2026-07-13** (no song forms). Resolutions: (finding-A) when a style IS locked, DROP the secondary cross-style section — same-style only, per goal #6 + the user's "not necessarily other styles"; keep cross-style ONLY when no style is locked (match.matched===false). (finding-B) null the role phrase when a same-style sibling shares NO transitions with the loop (no false "variation" claim — just name + level). Re-pin smoke §8 labels ('shares I7→V7'→'shorter form' etc.; scores stable) | engineering | claimed | D-72 | `src/components/RelatedProgressions.jsx`, `scripts/smoke.mjs` (§8 re-pin) | same-style-only when locked; honest cross-style only when unlocked; role phrase honest (finding-B); build + smoke green |
+| D-73 | **"Try this" chord-substitution feature** design (engine rules + UI): for a loop chord `{rootPc,quality}` in the detected key/style, a SMALL curated set (~3-4) of alternative chords — recommend the categories (relative/diatonic-third sub, borrowed-minor colour e.g. IV→iv, extension/colour e.g. maj7/add9/sus, a circle-of-fifths / secondary-dominant move) — each with a plain one-line WHY that teaches. Concrete worked examples for the user's Am–C–F case (both A-minor and C-major readings), arithmetically correct (the gate WILL recompute). The UI surface: where it mounts in the jam dashboard (per-station in the rail? a "Try this" line under the loop? — decide, keep it glanceable, tappable→ChordDetailModal), honest circle-of-fifths tie-in (a lens for the relative/neighbour subs, NOT claimed for borrowed/extension), edge states (no key / atonal), keep-it-simple (learnable, not a reharm engine). Use a SEPARATE component (disjoint from RelatedProgressions.jsx). No user gate: pick strongest, ≥2 rejected alternatives | design | ready | — | `docs/design/try-this-subs.md` | substitution categories + rules + why-copy spec'd and arithmetically honest; Am–C–F worked; UI surface + mount decided; L-73/L-74 bounded |
+| L-73 | Substitution engine: `suggestSubstitutions({rootPc,quality}, keyInfo, opts?)` in `src/lib/theory.js` (additive) → `[{rootPc, quality, label, why, category}]` per D-73's rules + a smoke truth-table (expected subs for known chords/keys, sabotage-proven like the resolveDegree guard) | engineering | backlog | D-73 | `src/lib/theory.js` (additive), `scripts/smoke.mjs` | engine returns musically-correct subs for all 14 qualities in-key; smoke truth-table bites; build green |
+| L-74 | "Try this" UI per D-73: new component consuming the engine, mounted in the jam dashboard per the doc; tappable→ChordDetailModal; tokens/AA; glanceable | engineering | backlog | D-73, L-73 | `src/components/TryThis.jsx` (new) + mount (per doc — re-lock) | try-this shows honest subs with why-copy for the live loop; zero-click; build + smoke green |
+| C-70 | Sprint-end sweep + PR #3 update (covers rail/licks + related + try-this) | quality | backlog | L-70, L-71, L-72, L-74 | (none — verification) | all green; PR updated |
 
-> Sequencing: D-70 → L-70 → L-71 (serial on JamGuide.jsx), and D-72 → L-72 run fully in PARALLEL (RelatedProgressions.jsx is disjoint). C-70 closes. Critic gates every task.
+> Sequencing (three parallel chains, file-disjoint): (A) D-70 → L-70 → L-71 (rail/licks); (B) D-72✓ → L-72 (related, same-style); (C) D-73 → L-73 → L-74 (try-this subs — theory.js + new TryThis.jsx, disjoint from A/B). C-70 closes after all. Critic gates every task.
 
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