From 76c4f32f9ef26bd60c1d91a59b351bafbc2c55ea Mon Sep 17 00:00:00 2001
From: Kevin <68612569+diyelectromusic@users.noreply.github.com>
Date: Thu, 27 Mar 2025 22:01:57 +0000
Subject: [PATCH] Simple implementation of MIDI CC 11 (Expression) as a live,
 MIDI only, multiplier for channel volume.

---
 src/mididevice.cpp | 11 ++++++++---
 src/minidexed.cpp  | 21 ++++++++++++++++++++-
 src/minidexed.h    |  2 ++
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/src/mididevice.cpp b/src/mididevice.cpp
index 216b466..40a3a75 100644
--- a/src/mididevice.cpp
+++ b/src/mididevice.cpp
@@ -37,14 +37,15 @@ LOGMODULE ("mididevice");
 #define MIDI_CHANNEL_AFTERTOUCH 0b1101   // right now Synth_Dexed just manage Channel Aftertouch not Polyphonic AT -> 0b1010
 #define MIDI_CONTROL_CHANGE	0b1011
 	#define MIDI_CC_BANK_SELECT_MSB		0
-	#define MIDI_CC_MODULATION			1
+	#define MIDI_CC_MODULATION		1
 	#define MIDI_CC_BREATH_CONTROLLER	2 
 	#define MIDI_CC_FOOT_PEDAL 		4
-	#define MIDI_CC_VOLUME				7
+	#define MIDI_CC_VOLUME			7
 	#define MIDI_CC_PAN_POSITION		10
+	#define MIDI_CC_EXPRESSION		11
 	#define MIDI_CC_BANK_SELECT_LSB		32
 	#define MIDI_CC_BANK_SUSTAIN		64
-	#define MIDI_CC_RESONANCE			71
+	#define MIDI_CC_RESONANCE		71
 	#define MIDI_CC_FREQUENCY_CUTOFF	74
 	#define MIDI_CC_REVERB_LEVEL		91
 	#define MIDI_CC_DETUNE_LEVEL		94
@@ -398,6 +399,10 @@ void CMIDIDevice::MIDIMessageHandler (const u8 *pMessage, size_t nLength, unsign
 							m_pSynthesizer->SetPan (pMessage[2], nTG);
 							break;
 		
+						case MIDI_CC_EXPRESSION:
+							m_pSynthesizer->SetExpression (pMessage[2], nTG);
+							break;
+		
 						case MIDI_CC_BANK_SELECT_MSB:
 							m_pSynthesizer->BankSelectMSB (pMessage[2], nTG);
 							break;
diff --git a/src/minidexed.cpp b/src/minidexed.cpp
index a485981..4d9a53c 100644
--- a/src/minidexed.cpp
+++ b/src/minidexed.cpp
@@ -72,6 +72,7 @@ CMiniDexed::CMiniDexed (CConfig *pConfig, CInterruptSystem *pInterrupt,
 		m_nVoiceBankIDMSB[i] = 0;
 		m_nProgram[i] = 0;
 		m_nVolume[i] = 100;
+		m_nExpression[i] = 127;
 		m_nPan[i] = 64;
 		m_nMasterTune[i] = 0;
 		m_nCutoff[i] = 99;
@@ -280,6 +281,7 @@ bool CMiniDexed::Initialize (void)
 		assert (m_pTG[i]);
 
 		SetVolume (100, i);
+		SetExpression (127, i);
 		ProgramChange (0, i);
 
 		m_pTG[i]->setTranspose (24);
@@ -648,11 +650,28 @@ void CMiniDexed::SetVolume (unsigned nVolume, unsigned nTG)
 	m_nVolume[nTG] = nVolume;
 
 	assert (m_pTG[nTG]);
-	m_pTG[nTG]->setGain (nVolume / 127.0f);
+	m_pTG[nTG]->setGain ((m_nVolume[nTG] * m_nExpression[nTG]) / (127.0f * 127.0f));
 
 	m_UI.ParameterChanged ();
 }
 
+void CMiniDexed::SetExpression (unsigned nExpression, unsigned nTG)
+{
+	nExpression=constrain((int)nExpression,0,127);
+
+	assert (nTG < CConfig::AllToneGenerators);
+	if (nTG >= m_nToneGenerators) return;  // Not an active TG
+
+	m_nExpression[nTG] = nExpression;
+
+	assert (m_pTG[nTG]);
+	m_pTG[nTG]->setGain ((m_nVolume[nTG] * m_nExpression[nTG]) / (127.0f * 127.0f));
+
+	// Expression is a "live performance" parameter only set
+	// via MIDI and not via the UI.
+	//m_UI.ParameterChanged ();
+}
+
 void CMiniDexed::SetPan (unsigned nPan, unsigned nTG)
 {
 	nPan=constrain((int)nPan,0,127);
diff --git a/src/minidexed.h b/src/minidexed.h
index bb6290b..6a7ef81 100644
--- a/src/minidexed.h
+++ b/src/minidexed.h
@@ -74,6 +74,7 @@ public:
 	void ProgramChange (unsigned nProgram, unsigned nTG);
 	void ProgramChangePerformance (unsigned nProgram);
 	void SetVolume (unsigned nVolume, unsigned nTG);
+	void SetExpression (unsigned nExpression, unsigned nTG);
 	void SetPan (unsigned nPan, unsigned nTG);			// 0 .. 127
 	void SetMasterTune (int nMasterTune, unsigned nTG);		// -99 .. 99
 	void SetCutoff (int nCutoff, unsigned nTG);			// 0 .. 99
@@ -261,6 +262,7 @@ private:
 	unsigned m_nVoiceBankIDMSBPerformance;
 	unsigned m_nProgram[CConfig::AllToneGenerators];
 	unsigned m_nVolume[CConfig::AllToneGenerators];
+	unsigned m_nExpression[CConfig::AllToneGenerators];
 	unsigned m_nPan[CConfig::AllToneGenerators];
 	int m_nMasterTune[CConfig::AllToneGenerators];
 	int m_nCutoff[CConfig::AllToneGenerators];