diff --git a/sound_algo/data_only/sections.scd b/sound_algo/data_only/sections.scd
new file mode 100644
index 0000000..b9473ff
--- /dev/null
+++ b/sound_algo/data_only/sections.scd
@@ -0,0 +1,140 @@
+// sections.scd — Ableton-scene-style section slots
+// 8 snapshot slots: armed clips + seq presets + harmony. Save, quantized recall,
+// next/prev chaining. Loaded after touchosc_feedback.scd (boot step 6h).
+// Additive, nil-guarded, idempotent on reload. Single top-level block.
+// Feedback: /scene/state <cur:int> <fill0:int> ... <fill7:int>
+(
+
+// -- Env init (nil-guarded; idempotent reload) --
+~lp = ~lp ? ();
+~lp[\sceneN]   = ~lp[\sceneN]   ? 8;
+~lp[\scenes]   = ~lp[\scenes]   ? Array.fill(~lp[\sceneN], nil);
+~lp[\sceneCur] = ~lp[\sceneCur] ? -1;
+
+// 16 clip symbols (same order as ~toscPatterns) ++ the two sequencers
+~scenePatterns = ~scenePatterns ? [
+    \kick, \hats,  \clap,  \perc,
+    \sub,  \acid,  \arp,   \lead,
+    \stab, \pad,   \ride,  \rim,
+    \tom,  \reese, \bells, \sweep,
+    \melseq, \rhythmseq
+];
+
+// -- ~scenePush : push /scene/state to all TouchOSC clients --
+~scenePush = ~scenePush ? {
+    var fills = ~lp[\scenes].collect({ |s| s.notNil.binaryValue });
+    ~toscSend !? { ~toscSend.valueArray(["/scene/state", ~lp[\sceneCur]] ++ fills) };
+};
+
+// -- ~sceneSave : snapshot current engine state into slot i --
+~sceneSave = ~sceneSave ? { |i|
+    (~lp.notNil and: { i >= 0 and: { i < (~lp[\sceneN] ? 8) } }).if({
+        ~lp[\scenes][i] = (
+            armed:   ~lp[\armed].copy,
+            melSel:  ~lp[\melSel],
+            rhySel:  ~lp[\rhySel],
+            harmony: (~ccHarmony.notNil).if({
+                (root:   ~ccHarmony[\root],
+                 scale:  ~ccHarmony[\scale],
+                 octave: ~ccHarmony[\octave],
+                 phrase: ~ccHarmony[\phrase])
+            }, { nil })
+        );
+        ~scenePush.();
+    });
+};
+
+// -- ~sceneLaunch : diff target armed-set vs current, fire ~lpArm per clip --
+// ~lpArm is already quantized: whole section transitions at next bar boundary.
+~sceneLaunch = ~sceneLaunch ? { |i|
+    var sc = ~lp[\scenes][i];
+    sc.notNil.if({
+        var target = sc[\armed];
+        ~scenePatterns.do { |nm|
+            var want = target.includes(nm);
+            var have = ~lp[\armed].includes(nm);
+            (want and: { have.not }).if({ ~lpArm.(nm.asString, true) });
+            (want.not and: { have }).if({ ~lpArm.(nm.asString, false) });
+        };
+        ~lp[\melSel] = sc[\melSel] ? ~lp[\melSel];
+        ~lp[\rhySel] = sc[\rhySel] ? ~lp[\rhySel];
+        (sc[\harmony].notNil and: { ~ccHarmony.notNil }).if({
+            [\root, \scale, \octave, \phrase].do { |k|
+                sc[\harmony][k] !? { |v| ~ccHarmony[k] = v };
+            };
+        });
+        ~lp[\sceneCur] = i;
+        ~scenePush.();
+    });
+};
+
+// -- ~sceneFilledIndices : list of non-nil slot indices --
+~sceneFilledIndices = ~sceneFilledIndices ? {
+    var idxs = [];
+    ~lp[\scenes].doWithIndex { |s, i| s.notNil.if({ idxs = idxs.add(i) }) };
+    idxs
+};
+
+// -- ~sceneNext : advance to next filled slot (wrap-around) --
+~sceneNext = ~sceneNext ? {
+    var cur   = ~lp[\sceneCur] ? -1;
+    var n     = ~lp[\sceneN]   ? 8;
+    var found = nil;
+    n.do { |offset|
+        var idx = (cur + 1 + offset) % n;
+        found.isNil.if({
+            ~lp[\scenes][idx].notNil.if({ found = idx });
+        });
+    };
+    found.notNil.if({ ~sceneLaunch.(found) });
+};
+
+// -- ~scenePrev : retreat to previous filled slot (wrap-around) --
+~scenePrev = ~scenePrev ? {
+    var cur   = ~lp[\sceneCur] ? -1;
+    var n     = ~lp[\sceneN]   ? 8;
+    var found = nil;
+    n.do { |offset|
+        var idx = ((cur - 1 - offset) % n + n) % n;
+        found.isNil.if({
+            ~lp[\scenes][idx].notNil.if({ found = idx });
+        });
+    };
+    found.notNil.if({ ~sceneLaunch.(found) });
+};
+
+// -- ~sceneClear : clear slot i; reset ~sceneCur if it was the active scene --
+~sceneClear = ~sceneClear ? { |i|
+    ~lp[\scenes][i] = nil;
+    (~lp[\sceneCur] == i).if({ ~lp[\sceneCur] = -1 });
+    ~scenePush.();
+};
+
+// -- OSCdefs (unique keys with \scene_ prefix; call ~toscTouch for feedback) --
+OSCdef(\scene_save, { |msg, time, addr|
+    ~toscTouch !? { ~toscTouch.(addr) };
+    ~sceneSave.(msg[1].asInteger);
+}, '/scene/save');
+
+OSCdef(\scene_launch, { |msg, time, addr|
+    ~toscTouch !? { ~toscTouch.(addr) };
+    ~sceneLaunch.(msg[1].asInteger);
+}, '/scene/launch');
+
+OSCdef(\scene_next, { |msg, time, addr|
+    ~toscTouch !? { ~toscTouch.(addr) };
+    ~sceneNext.();
+}, '/scene/next');
+
+OSCdef(\scene_prev, { |msg, time, addr|
+    ~toscTouch !? { ~toscTouch.(addr) };
+    ~scenePrev.();
+}, '/scene/prev');
+
+OSCdef(\scene_clear, { |msg, time, addr|
+    ~toscTouch !? { ~toscTouch.(addr) };
+    ~sceneClear.(msg[1].asInteger);
+}, '/scene/clear');
+
+"[sections] ready".postln;
+)
diff --git a/sound_algo/data_only/test/test_sections.scd b/sound_algo/data_only/test/test_sections.scd
new file mode 100644
index 0000000..ca3f2fa
--- /dev/null
+++ b/sound_algo/data_only/test/test_sections.scd
@@ -0,0 +1,59 @@
+// Headless test for sections.scd
+// Run: /Applications/SuperCollider.app/Contents/MacOS/sclang \
+//        sound_algo/data_only/test/test_sections.scd
+// Expected output: TEST PASS  (with no ERROR lines from sections.scd)
+//
+// Server is NOT booted. ~lpArm, ~toscSend, ~ccHarmony are stubbed.
+(
+var featureFile = PathName(thisProcess.nowExecutingPath).pathOnly
+    ++ "../sections.scd";
+var pass = true;
+
+// Minimal dummy environment matching shapes expected by sections.scd
+~lp = (
+    armed:    Set[\kick],
+    melSel:   0,
+    rhySel:   0,
+    clock:    TempoClock.default,
+    melodies: [[0]],
+    rhythms:  [(name: "x", k: "", s: "", h: "")]
+);
+
+// Stubs — no server, no real transport
+~lpArm    = { |n, o| };
+~ccHarmony = (root: 40, scale: \minor, octave: 1, phrase: 0);
+~toscSend  = { |...a| };
+
+// Load the feature file (synchronous; stubs already in place)
+featureFile.load;
+
+// Assert public API functions were wired
+pass = pass and: { ~sceneSave.notNil   };
+pass = pass and: { ~sceneLaunch.notNil };
+pass = pass and: { ~sceneNext.notNil   };
+
+// ~sceneSave.(0) must populate slot 0
+try { ~sceneSave.(0) } { |e|
+    pass = false;
+    ("EXCEPTION in ~sceneSave: " ++ e.class.name).postln;
+};
+pass = pass and: { ~lp[\scenes][0].notNil };
+
+// ~sceneLaunch.(0) must not raise
+try { ~sceneLaunch.(0) } { |e|
+    pass = false;
+    ("EXCEPTION in ~sceneLaunch: " ++ e.class.name).postln;
+};
+
+// ~sceneNext must not raise (slot 0 filled; wraps back and launches 0 again)
+try { ~sceneNext.() } { |e|
+    pass = false;
+    ("EXCEPTION in ~sceneNext: " ++ e.class.name).postln;
+};
+
+pass.if(
+    { "TEST PASS".postln },
+    { "TEST FAIL".postln }
+);
+0.exit;
+)