diff --git a/src/minidexed.cpp b/src/minidexed.cpp
index 762cf3d..ce8f4d9 100644
--- a/src/minidexed.cpp
+++ b/src/minidexed.cpp
@@ -291,6 +291,20 @@ void CMiniDexed::SetVolume (unsigned nVolume, unsigned nTG)
 	m_UI.VolumeChanged (nVolume, nTG);
 }
 
+void CMiniDexed::SetMasterTune (int nMasterTune, unsigned nTG)
+{
+	if (!(-99 <= nMasterTune && nMasterTune <= 99))
+	{
+		return;
+	}
+
+	assert (nTG < CConfig::ToneGenerators);
+	assert (m_pTG[nTG]);
+	m_pTG[nTG]->setMasterTune ((int8_t) nMasterTune);
+
+	m_UI.MasterTuneChanged (nMasterTune, nTG);
+}
+
 void CMiniDexed::SetMIDIChannel (uint8_t uchChannel, unsigned nTG)
 {
 	assert (nTG < CConfig::ToneGenerators);
diff --git a/src/minidexed.h b/src/minidexed.h
index 144e53b..b4dccca 100644
--- a/src/minidexed.h
+++ b/src/minidexed.h
@@ -59,6 +59,7 @@ public:
 	void BankSelectLSB (unsigned nBankLSB, unsigned nTG);
 	void ProgramChange (unsigned nProgram, unsigned nTG);
 	void SetVolume (unsigned nVolume, unsigned nTG);
+	void SetMasterTune (int nMasterTune, unsigned nTG);		// -99 .. 99
 	void SetMIDIChannel (uint8_t uchChannel, unsigned nTG);
 
 	void keyup (int16_t pitch, unsigned nTG);
diff --git a/src/userinterface.cpp b/src/userinterface.cpp
index ee9bf4b..38bb3b6 100644
--- a/src/userinterface.cpp
+++ b/src/userinterface.cpp
@@ -44,6 +44,7 @@ CUserInterface::CUserInterface (CMiniDexed *pMiniDexed, CGPIOManager *pGPIOManag
 		m_nBank[nTG] = 0;
 		m_nProgram[nTG] = 0;
 		m_nVolume[nTG] = 0;
+		m_nMasterTune[nTG] = 0;
 		m_uchMIDIChannel[nTG] = CMIDIDevice::Disabled;
 	}
 }
@@ -184,6 +185,25 @@ void CUserInterface::VolumeChanged (unsigned nVolume, unsigned  nTG)
 	}
 }
 
+void CUserInterface::MasterTuneChanged (int nMasterTune, unsigned  nTG)
+{
+	assert (-99 <= nMasterTune && nMasterTune <= 99);
+	assert (nTG < CConfig::ToneGenerators);
+	m_nMasterTune[nTG] = nMasterTune;
+
+	if (   m_UIMode == UIModeMasterTune
+	    && m_nTG == nTG)
+	{
+		CString TG;
+		TG.Format ("TG%u", nTG+1);
+
+		CString String;
+		String.Format ("%d", nMasterTune);
+
+		DisplayWrite (TG, "MASTER TUNE", "DETUNE", (const char *) String);
+	}
+}
+
 void CUserInterface::MIDIChannelChanged (uint8_t uchChannel, unsigned  nTG)
 {
 	assert (nTG < CConfig::ToneGenerators);
@@ -344,6 +364,20 @@ void CUserInterface::EncoderEventHandler (CKY040::TEvent Event)
 		m_pMiniDexed->SetVolume (nVolume, m_nTG);
 		} break;
 
+	case UIModeMasterTune: {
+		int nMasterTune = m_nMasterTune[m_nTG] + nStep;
+		if (nMasterTune < -99)
+		{
+			nMasterTune = -99;
+		}
+		else if (nMasterTune > 99)
+		{
+			nMasterTune = 99;
+		}
+
+		m_pMiniDexed->SetMasterTune (nMasterTune, m_nTG);
+		} break;
+
 	case UIModeMIDI:
 		if ((uint8_t) (m_uchMIDIChannel[m_nTG] + nStep) < CMIDIDevice::ChannelUnknown)
 		{
diff --git a/src/userinterface.h b/src/userinterface.h
index 05d7d61..06b3448 100644
--- a/src/userinterface.h
+++ b/src/userinterface.h
@@ -42,6 +42,7 @@ public:
 	void BankSelected (unsigned nBankLSB, unsigned  nTG);		// 0 .. 127
 	void ProgramChanged (unsigned nProgram, unsigned  nTG);		// 0 .. 127
 	void VolumeChanged (unsigned nVolume, unsigned  nTG);		// 0 .. 127
+	void MasterTuneChanged (int nMasterTune, unsigned  nTG);	// -99 .. 99
 	void MIDIChannelChanged (uint8_t uchChannel, unsigned  nTG);
 
 private:
@@ -65,6 +66,7 @@ private:
 		UIModeVoiceSelect = UIModeStart,
 		UIModeBankSelect,
 		UIModeVolume,
+		UIModeMasterTune,
 		UIModeMIDI,
 		UIModeUnknown
 	};
@@ -85,6 +87,7 @@ private:
 	unsigned m_nBank[CConfig::ToneGenerators];
 	unsigned m_nProgram[CConfig::ToneGenerators];
 	unsigned m_nVolume[CConfig::ToneGenerators];
+	int m_nMasterTune[CConfig::ToneGenerators];
 	uint8_t m_uchMIDIChannel[CConfig::ToneGenerators];
 };