tap · tap · Jul 19, 2026 · Jul 18, 2026 · Jul 18, 2026 · Jul 19, 2026
diff --git a/REVIVAL.md b/REVIVAL.md
@@ -1058,6 +1058,36 @@ GitHub Actions CI.
   network, eight voices* (the `tr808_*` headers — the bridged-T solved on its states,
   the calibration lesson), and *Time as a function of phase* (`step_seq.h` — the O(1)
   derivation, gate-hold look-ahead, armed-recall re-derivation).
+- ✅ **Net-new object — `tap.vca~` (2026-07-18).** The 303's transistor VCA stage, lifted out
+  where it can amplify anything. Kernel: **`vca.h`** (`taptools::vca`) — the two-circuit `svf.h`
+  idiom applied to a gain stage: `clean` is the pure linear multiply (bit-identical to `*~`),
+  `warm` is the one-transistor class-A saturator `S(v) = (tanh(d·v+b) − tanh(b)) / (d·sech²(b))`
+  (stock `d=2.0`, `b=0.3` — the probe-calibrated 303 constants, now exposed as `drive`/`bias`),
+  applied to the post-gain signal so the even-harmonic warmth and compression **track the control
+  voltage** the way a discrete VCA does and a multiply cannot, plus an optional output-coupling DC
+  block (`dcblock`) for the shaper's signal-dependent offset. **`tb303_voice.h` was refactored to
+  compose `vca::shape()`** — one implementation shared between `tap.303~` and the standalone; the
+  voice keeps its own Open303 output high-pass and gain, so the extraction left it **bit-identical**
+  (pinned by `tests/vca_test.cpp`, which matches `shape()` to the old inline formula and re-runs the
+  303 warm-vs-clean scenarios). Wrapper `tap.vca_tilde` (audio in + signal/float gain CV in),
+  `circuit clean|warm` + `drive`/`bias`/`dcblock`/`bypass`/`mute`, the full vertical slice (maxref +
+  help patcher). Remaining: runtime validation in Max.
+- ✅ **The 808 swing-VCA harmonics — `vca.h` `swing` mode + the noise voices (2026-07-18).** The
+  first piece of the flagged 808 circuit-sim work, and the lowest-risk one: the swing-type VCA's
+  "many high harmonics" (Service Notes, RS/CL VCA), which `swing_vca()` had modeled as a flat
+  `x·env`. Kernel: **`vca.h` gains `mode_swing`** — a symmetric (odd-harmonic) `tanh(d·v)/d`
+  saturator, unity-slope-at-0 so quiet tails stay clean and hot transients pick up grit and
+  compression, no DC (symmetric → no coupling block needed). One implementation: a static
+  `vca::swing_shape(v, drive)` that both `mode_swing` and **`swing_vca(x, env, drive)`** route
+  through. **`drive` defaults to 0 → the exact linear passthru**, so every calibrated 808 voice
+  stays **bit-identical** until it opts in (the full existing `tr808_*` suite passes unchanged; the
+  snare test adds an explicit off-is-bit-identical / on-saturates-and-compresses scenario). Wired
+  into the three noise-path voices — **snare** (snappy), **clap** (CP + maracas output), **tom**
+  (noise "reverberation") — each exposing a `drive` circuit-bend attribute (0..12). `tap.vca~` gains
+  the matching `circuit swing`. The heavier WDF `@circuit` pass (the kick bridged-T etc.) stays
+  where the field guide left it — gated on an A/B showing an audible delta the informed model misses,
+  which the DAFx-14 finding suggests may never open. Remaining: A/B calibration of the swing `drive`
+  against reference, and runtime validation in Max.
 
 ---
 

diff --git a/docs/tap.808.clap~.maxref.xml b/docs/tap.808.clap~.maxref.xml
@@ -90,6 +90,15 @@
 				it, leaving only the three teeth; above 1 exaggerates the wash.
 			</description>
 		</attribute>
+		<attribute name="drive" get="1" set="1" type="float" size="1">
+			<digest>Circuit bend: swing-VCA drive on the output VCA (default 0 = linear)</digest>
+			<description>
+				Swing-VCA drive on the output VCA, 0..12, for both the clap and maracas models.
+				0 is the calibrated linear model (default); higher engages the swing VCA's
+				symmetric harmonic saturation — grit and compression that ride the envelope.
+				See tap.vca~ (the swing circuit).
+			</description>
+		</attribute>
 		<attribute name="seed" get="1" set="1" type="int" size="1">
 			<digest>Noise seed (deterministic)</digest>
 			<description>

diff --git a/docs/tap.808.snare~.maxref.xml b/docs/tap.808.snare~.maxref.xml
@@ -99,6 +99,15 @@
 				(~238/476 Hz) — about 1.4 here.
 			</description>
 		</attribute>
+		<attribute name="drive" get="1" set="1" type="float" size="1">
+			<digest>Circuit bend: swing-VCA drive on the snappy path (default 0 = linear)</digest>
+			<description>
+				Swing-VCA drive on the snappy noise path, 0..12. 0 is the calibrated linear
+				model (default); higher engages the swing VCA's symmetric harmonic saturation —
+				grit and compression that ride the snappy envelope, hardest on the transient
+				crack. See tap.vca~ (the swing circuit).
+			</description>
+		</attribute>
 		<attribute name="seed" get="1" set="1" type="int" size="1">
 			<digest>Noise seed (deterministic)</digest>
 			<description>

diff --git a/docs/tap.808.tom~.maxref.xml b/docs/tap.808.tom~.maxref.xml
@@ -91,6 +91,15 @@
 			<digest>Output level</digest>
 			<description>Output level, 0..1 (default 1).</description>
 		</attribute>
+		<attribute name="drive" get="1" set="1" type="float" size="1">
+			<digest>Circuit bend: swing-VCA drive on the noise layer (default 0 = linear)</digest>
+			<description>
+				Swing-VCA drive on the noise "reverberation" layer, 0..12 (toms only — congas
+				have no noise layer). 0 is the calibrated linear model (default); higher engages
+				the swing VCA's symmetric harmonic saturation riding the noise envelope. See
+				tap.vca~ (the swing circuit).
+			</description>
+		</attribute>
 		<attribute name="seed" get="1" set="1" type="int" size="1">
 			<digest>Noise seed (toms; deterministic)</digest>
 			<description>Seed (&gt;= 1) for the tom noise layer; give mc. instances different seeds.</description>

diff --git a/docs/tap.vca~.maxref.xml b/docs/tap.vca~.maxref.xml
@@ -0,0 +1,108 @@
+<?xml version="1.0" encoding="utf-8" standalone="yes"?>
+<?xml-stylesheet href="./_c74_ref.xsl" type="text/xsl"?>
+
+<c74object name="tap.vca~" module="msp" category="TapTools, MSP Modifiers">
+
+	<digest>
+		Voltage-controlled amplifier — clean multiply or warm transistor stage
+	</digest>
+
+	<description>
+		The <o>tap.vca~</o> object is a voltage-controlled amplifier. The left inlet is the
+		audio; the right inlet is the gain / control voltage — a signal for true per-sample
+		modulation, or a float to set the <at>gain</at> attribute. The <at>circuit</at>
+		attribute chooses the character: <b>clean</b> is a pure linear multiply, bit-identical
+		to <o>*~</o> — transparent, with no added harmonics or DC. <b>warm</b> is the Roland
+		TB-303's one-transistor class-A VCA stage — the same kernel <o>tap.303~</o> runs — a
+		biased, slope-normalized tanh applied after the gain: quiet signals stay essentially
+		clean, while hot signals pick up even-harmonic warmth and gentle compression that track
+		the control voltage, the way a discrete VCA does and a plain multiply cannot. An output
+		DC block (the <at>dcblock</at> attribute) sheds the shaped signal's DC offset, as the
+		hardware's output coupling capacitor does. The <at>drive</at> and <at>bias</at>
+		attributes shape the warm circuit (stock at the 303's values). One channel per object;
+		wrap in mc. for multichannel.
+	</description>
+
+
+	<!--METADATA-->
+	<metadatalist>
+		<metadata name="author">74 Objects</metadata>
+		<metadata name="tag">TapTools</metadata>
+		<metadata name="tag">Audio</metadata>
+		<metadata name="tag">MSP Modifiers</metadata>
+		<metadata name="tag">Multichannel</metadata>
+		<metadata name="tag">64-bit</metadata>
+	</metadatalist>
+
+
+	<!--MESSAGES-->
+	<methodlist>
+		<method name="signal">
+			<arglist/>
+			<description>In the left inlet, the audio to amplify. In the right inlet, the gain /
+			control voltage (linear), applied per sample.</description>
+		</method>
+		<method name="float">
+			<arglist>
+				<arg name="gain" type="float" optional="0" id="1" />
+			</arglist>
+			<description>In the right inlet, sets the <at>gain</at> attribute. Ignored while a
+			signal is connected to that inlet.</description>
+		</method>
+		<method name="clear">
+			<arglist/>
+			<description>Reset the stage's DC-block state.</description>
+		</method>
+	</methodlist>
+
+
+	<!--ATTRIBUTES-->
+	<attributelist>
+		<attribute name="circuit" get="1" set="1" type="symbol" size="1">
+			<description>Amplifier circuit: clean (default, the pure linear multiply,
+			bit-identical to *~), warm (the TB-303 one-transistor class-A stage — asymmetric
+			biased-tanh saturation with even harmonics, plus the output DC block), or swing (the
+			TR-808 swing-type VCA — symmetric saturation with odd harmonics and no DC, the same
+			stage the 808 noise voices use). In warm and swing the warmth and compression ride the
+			control voltage; bias is ignored by swing.</description>
+		</attribute>
+		<attribute name="gain" get="1" set="1" type="float" size="1">
+			<description>Linear gain applied when no signal is connected to the right inlet. A
+			signal in the right inlet overrides this per sample.</description>
+		</attribute>
+		<attribute name="drive" get="1" set="1" type="float" size="1">
+			<description>Drive into the transistor stage's tanh for the warm and swing circuits
+			(0.1-12; default 2, the stock 303 value). Higher drive means more harmonics and more
+			compression. Ignored by the clean circuit.</description>
+		</attribute>
+		<attribute name="bias" get="1" set="1" type="float" size="1">
+			<description>Warm-circuit operating-point bias (-2..2; default 0.3, the stock 303
+			value). The asymmetry that produces even harmonics; 0 is a symmetric (odd-only)
+			shaper. Ignored by the clean circuit.</description>
+		</attribute>
+		<attribute name="dcblock" get="1" set="1" type="int" size="1">
+			<description>Warm-circuit output DC block (default on). The biased shaper leaves a
+			signal-dependent DC offset on AC material; this one-pole coupling high-pass removes
+			it, as the hardware's output capacitor does. Turn off to hear the raw
+			asymmetry.</description>
+		</attribute>
+		<attribute name="bypass" get="1" set="1" type="int" size="1">
+			<description>Pass the input through unprocessed.</description>
+		</attribute>
+		<attribute name="mute" get="1" set="1" type="int" size="1">
+			<description>Silence the output.</description>
+		</attribute>
+	</attributelist>
+
+
+	<!--SEEALSO-->
+	<seealsolist>
+		<seealso name="tap.303~"/>
+		<seealso name="tap.crossfade~"/>
+		<seealso name="tap.pan~"/>
+		<seealso name="*~"/>
+		<seealso name="gain~"/>
+	</seealsolist>
+
+
+</c74object>