Starting Env: envelope/pitch detector as VCV Rack module.

Beginning the panel design for a working VCV Rack module
based on Surge XT / Tree Monster's pitch and envelope detectors.
I'm not using their algorithm directly, but reading their code
for the basic idea:

Bandpass filter the input audio for each channel.
This rejects DC and other signals below audible range.
Also filter out very high frequencies to reject noise.

Count ascending and descending zero-crossing intervals,
called wavelengths. Convert wavelengths to pitch V/OCT.

src/sapphire_panel.cpp

@@ -69,6 +69,9 @@ namespace Sapphire
             {"span_slider",            {  30.480,   46.000}},
             {"stif_slider",            {  19.240,   46.000}},
             }},
+        { "env", {
+            {"_panel",                 {  30.480,  128.500}},
+            }},
         { "frolic", {
             {"_panel",                 {  20.320,  128.500}},
             {"chaos_atten",            {   5.160,   68.000}},

util/make_sapphire_svg.py

@@ -1834,6 +1834,24 @@ def GenerateTubeUnit(cdict:Dict[str, ControlLayer], title:str, symbol:str) -> in
 
     return 0
 
+
+def GenerateEnvPitchPanel(cdict:Dict[str, ControlLayer], target:Target) -> int:
+    name = 'env'
+    PANEL_WIDTH = 6
+    svgFileName = SvgFileName(name, target)
+    panel = Panel(PANEL_WIDTH)
+    cdict[cdict_name(name, target)] = controls = ControlLayer(panel)
+    pl = Element('g', 'PanelLayer')
+    defs = Element('defs')
+    pl.append(defs)
+    panel.append(pl)
+    with Font(SAPPHIRE_FONT_FILENAME) as font:
+        pl.append(BorderRect(PANEL_WIDTH, SAPPHIRE_PANEL_COLOR, SAPPHIRE_BORDER_COLOR))
+        pl.append(CenteredGemstone(panel))
+        pl.append(ModelNamePath(panel, font, name))
+    return Save(panel, svgFileName)
+
+
 if __name__ == '__main__':
     cdict:Dict[str, ControlLayer] = {}
     sys.exit(
@@ -1866,6 +1884,7 @@ def GenerateTubeUnit(cdict:Dict[str, ControlLayer], title:str, symbol:str) -> in
         GeneratePopPanel(cdict) or
         GenerateElastikaPanel(cdict, Target.VcvRack) or
         GenerateElastikaPanel(cdict, Target.Lite) or
+        GenerateEnvPitchPanel(cdict, Target.VcvRack) or
         GenerateTubeUnit(cdict, 'tube unit', 'tubeunit') or
         GenerateTubeUnit(cdict, 'tube monster', 'tubemonster') or
         SaveControls(cdict) or