Report the instrument's automatable parameters to the host under a frozen id table, in signal-flow order, with real units

42 of 44 ids issued: pitch key-track and Trigger length stay reserved
pending a live path. Master gain reclassified Live — it never reloaded.

src/core/instrument/engine/filter/filter_params.cpp

@@ -52,6 +52,13 @@ float filterDriveDepthFromNorm(float norm) {
     return static_cast<float>(kFilterDriveDepthMax * n * n);
 }
 
+float filterNormFromDriveDepth(float depth) {
+    if (!(depth > 0.0f)) return 0.0f;  // also catches NaN
+    if (depth >= kFilterDriveDepthMax) return 1.0f;
+    return static_cast<float>(
+        std::sqrt(static_cast<double>(depth) / static_cast<double>(kFilterDriveDepthMax)));
+}
+
 float filterNormFromQ(float q) {
     if (!(q > kFilterQMin)) return 0.0f;
     if (q >= kFilterQMax) return 1.0f;

src/core/instrument/engine/filter/filter_params.h

@@ -49,4 +49,9 @@ float filterNormFromQ(float q);
 // linear rather than merely close.
 float filterDriveDepthFromNorm(float norm);
 
+// Exact inverse of filterDriveDepthFromNorm; out-of-range depth clamps to 0 or 1. The analytic
+// inverse of a frozen law is not a change to it — it has the standing the two inverses above
+// already have.
+float filterNormFromDriveDepth(float depth);
+
 }  // namespace reasampler::instrument::engine::filter

src/core/instrument/engine/master_gain.cpp

@@ -6,7 +6,6 @@
 
 #include <algorithm>
 #include <cmath>
-#include <cstdio>
 #include <limits>
 
 namespace reasampler::instrument::engine {
@@ -37,15 +36,4 @@ double masterGainNormFromLinear(double linear) {
     return masterGainNormFromDb(20.0 * std::log10(linear));
 }
 
-void formatMasterGainLabel(double norm, char* buf, std::size_t len) {
-    if (!buf || len == 0) return;
-    norm = clamp01(norm);
-    if (norm <= 0.0) {
-        std::snprintf(buf, len, "-inf");
-        return;
-    }
-    const double db = masterGainDbFromNorm(norm);
-    std::snprintf(buf, len, "%+.1fdB", db);
-}
-
 }  // namespace reasampler::instrument::engine

src/core/instrument/engine/master_gain.h

@@ -7,8 +7,6 @@
 
 #pragma once
 
-#include <cstddef>
-
 namespace reasampler::instrument::engine {
 
 // norm 0 is -inf (true zero); norm just above 0 starts at the finite floor kMasterGainMinDb
@@ -31,8 +29,4 @@ double masterGainLinearFromNorm(double norm);
 // true-zero and the floor aren't representable on the knob. Out-of-range/non-finite clamps.
 double masterGainNormFromLinear(double linear);
 
-// "-inf" at the bottom, else a signed one-decimal dB string ("-12.0dB", "+2.4dB").
-// Writes at most `len` bytes including the terminator.
-void formatMasterGainLabel(double norm, char* buf, std::size_t len);
-
 }  // namespace reasampler::instrument::engine