diff --git a/src/sound/mididevices/music_opl_mididevice.cpp b/src/sound/mididevices/music_opl_mididevice.cpp
index fe09e0448..d584d3ebd 100644
--- a/src/sound/mididevices/music_opl_mididevice.cpp
+++ b/src/sound/mididevices/music_opl_mididevice.cpp
@@ -87,7 +87,7 @@ OPLMIDIDevice::OPLMIDIDevice(const char *args)
 	uint8_t filehdr[8];
 	data.Read(filehdr, 8);
 	if (memcmp(filehdr, "#OPL_II#", 8)) I_Error("Corrupt GENMIDI lump");
-	data.Read(OPLinstruments, sizeof(genmidi_instr_t) * GENMIDI_NUM_TOTAL);
+	data.Read(OPLinstruments, sizeof(GenMidiInstrument) * GENMIDI_NUM_TOTAL);
 	SampleRate = (int)OPL_SAMPLE_RATE;
 }
 
diff --git a/src/sound/oplsynth/genmidi.h b/src/sound/oplsynth/genmidi.h
index 76ac26a96..f315f8245 100644
--- a/src/sound/oplsynth/genmidi.h
+++ b/src/sound/oplsynth/genmidi.h
@@ -11,7 +11,7 @@ struct genmidi_op_t
 	uint8_t level;
 } FORCE_PACKED;
 
-struct genmidi_voice_t
+struct GenMidiVoice
 {
 	genmidi_op_t modulator;
 	uint8_t feedback;
@@ -21,12 +21,12 @@ struct genmidi_voice_t
 } FORCE_PACKED;
 
 
-struct genmidi_instr_t
+struct GenMidiInstrument
 {
 	uint16_t flags;
 	uint8_t fine_tuning;
 	uint8_t fixed_note;
-	genmidi_voice_t voices[2];
+	GenMidiVoice voices[2];
 } FORCE_PACKED;
 
 #pragma pack(pop)
diff --git a/src/sound/oplsynth/musicblock.cpp b/src/sound/oplsynth/musicblock.cpp
index e0a231476..9a2c0d93f 100644
--- a/src/sound/oplsynth/musicblock.cpp
+++ b/src/sound/oplsynth/musicblock.cpp
@@ -90,11 +90,11 @@ int musicBlock::replaceExistingVoice()
 //
 //----------------------------------------------------------------------------
 
-void musicBlock::voiceKeyOn(uint32_t slot, uint32_t channo, genmidi_instr_t *instrument, uint32_t instrument_voice, uint32_t key, uint32_t volume)
+void musicBlock::voiceKeyOn(uint32_t slot, uint32_t channo, GenMidiInstrument *instrument, uint32_t instrument_voice, uint32_t key, uint32_t volume)
 {
 	struct OPLVoice *voice = &voices[slot];
 	auto &channel = oplchannels[channo];
-	genmidi_voice_t *gmvoice;
+	GenMidiVoice *gmvoice;
 
 	voice->index = channo;
 	voice->key = key;
@@ -159,7 +159,7 @@ void musicBlock::noteOn(uint32_t channel, uint8_t key, int volume)
 		return;
 	}
 	uint32_t note;
-	genmidi_instr_t *instrument;
+	GenMidiInstrument *instrument;
 
 	// Percussion channel is treated differently.
 	if (channel == CHAN_PERCUSSION)
diff --git a/src/sound/oplsynth/musicblock.h b/src/sound/oplsynth/musicblock.h
index 1f13aa01f..e806a45e6 100644
--- a/src/sound/oplsynth/musicblock.h
+++ b/src/sound/oplsynth/musicblock.h
@@ -10,8 +10,8 @@ struct OPLVoice
 	unsigned int key;			// The midi key that this voice is playing.
 	unsigned int note;			// The note being played.  This is normally the same as the key, but if the instrument is a fixed pitch instrument, it is different.
 	unsigned int note_volume;	// The volume of the note being played on this channel.
-	genmidi_instr_t *current_instr;	// Currently-loaded instrument data
-	genmidi_voice_t *current_instr_voice;// The voice number in the instrument to use. This is normally set to the instrument's first voice; if this is a double voice instrument, it may be the second one
+	GenMidiInstrument *current_instr;	// Currently-loaded instrument data
+	GenMidiVoice *current_instr_voice;// The voice number in the instrument to use. This is normally set to the instrument's first voice; if this is a double voice instrument, it may be the second one
 	bool sustained;
 	int8_t	fine_tuning;
 	int	pitch;
@@ -21,13 +21,10 @@ struct musicBlock {
 	musicBlock();
 	~musicBlock();
 
-	uint8_t *score;
-	uint8_t *scoredata;
-	int playingcount;
 	OPLChannel oplchannels[NUM_CHANNELS];
 	OPLio *io;
 
-	struct genmidi_instr_t OPLinstruments[GENMIDI_NUM_TOTAL];
+	struct GenMidiInstrument OPLinstruments[GENMIDI_NUM_TOTAL];
 
 	void changeModulation(uint32_t id, int value);
 	void changeSustain(uint32_t id, int value);
@@ -50,9 +47,18 @@ protected:
 
 	int findFreeVoice();
 	int replaceExistingVoice();
-	void voiceKeyOn(uint32_t slot, uint32_t channo, genmidi_instr_t *instrument, uint32_t instrument_voice, uint32_t, uint32_t volume);
+	void voiceKeyOn(uint32_t slot, uint32_t channo, GenMidiInstrument *instrument, uint32_t instrument_voice, uint32_t, uint32_t volume);
 	int releaseVoice(uint32_t slot, uint32_t killed);
 
 	friend class Stat_opl;
 
 };
+
+enum ExtCtrl {
+	ctrlRPNHi,
+	ctrlRPNLo,
+	ctrlNRPNHi,
+	ctrlNRPNLo,
+	ctrlDataEntryHi,
+	ctrlDataEntryLo,
+};
diff --git a/src/sound/oplsynth/opl_mus_player.h b/src/sound/oplsynth/opl_mus_player.h
index a8ace69d2..52ef4be76 100644
--- a/src/sound/oplsynth/opl_mus_player.h
+++ b/src/sound/oplsynth/opl_mus_player.h
@@ -1,5 +1,5 @@
 #include "critsec.h"
-#include "muslib.h"
+#include "musicblock.h"
 
 class FileReader;
 
@@ -18,6 +18,9 @@ protected:
 	virtual int PlayTick() = 0;
 	void OffsetSamples(float *buff, int count);
 
+	uint8_t *score;
+	uint8_t *scoredata;
+	int playingcount;
 	double NextTickIn;
 	double SamplesPerTick;
 	int NumChips;
diff --git a/src/sound/oplsynth/oplio.cpp b/src/sound/oplsynth/oplio.cpp
index 68b769db4..1229a5bbf 100644
--- a/src/sound/oplsynth/oplio.cpp
+++ b/src/sound/oplsynth/oplio.cpp
@@ -353,7 +353,7 @@ static uint8_t volumetable[128] = {
 	120, 121, 121, 122, 122, 123, 123, 123,
 	124, 124, 125, 125, 126, 126, 127, 127};
 
-void OPLio::WriteVolume(uint32_t channel, struct genmidi_voice_t *voice, uint32_t vol1, uint32_t vol2, uint32_t vol3)
+void OPLio::WriteVolume(uint32_t channel, struct GenMidiVoice *voice, uint32_t vol1, uint32_t vol2, uint32_t vol3)
 {
 	if (voice != nullptr)
 	{
@@ -392,7 +392,7 @@ void OPLio::WriteVolume(uint32_t channel, struct genmidi_voice_t *voice, uint32_
 //
 //----------------------------------------------------------------------------
 
-void OPLio::WritePan(uint32_t channel, struct genmidi_voice_t *voice, int pan)
+void OPLio::WritePan(uint32_t channel, struct GenMidiVoice *voice, int pan)
 {
 	if (voice != 0)
 	{
@@ -418,7 +418,7 @@ void OPLio::WritePan(uint32_t channel, struct genmidi_voice_t *voice, int pan)
 //
 //----------------------------------------------------------------------------
 
-void OPLio::WriteTremolo(uint32_t channel, struct genmidi_voice_t *voice, bool vibrato)
+void OPLio::WriteTremolo(uint32_t channel, struct GenMidiVoice *voice, bool vibrato)
 {
 	int val1 = voice->modulator.tremolo, val2 = voice->carrier.tremolo;
 	if (vibrato)
@@ -478,7 +478,7 @@ void OPLio::LoadOperatorData(uint32_t channel, int op_index, genmidi_op_t *data,
 //
 //----------------------------------------------------------------------------
 
-void OPLio::WriteInstrument(uint32_t channel, struct genmidi_voice_t *voice, bool vibrato)
+void OPLio::WriteInstrument(uint32_t channel, struct GenMidiVoice *voice, bool vibrato)
 {
 	bool modulating = (voice->feedback & 0x01) == 0;
 
diff --git a/src/sound/oplsynth/oplio.h b/src/sound/oplsynth/oplio.h
index 94ad8b2f0..93b7e281c 100644
--- a/src/sound/oplsynth/oplio.h
+++ b/src/sound/oplsynth/oplio.h
@@ -54,7 +54,7 @@ enum
 
 };
 
-struct genmidi_voice_t;
+struct GenMidiVoice;
 
 struct OPLio 
 {
@@ -64,10 +64,10 @@ struct OPLio
 	void LoadOperatorData(uint32_t channel, int op_index, genmidi_op_t *op_data, bool maxlevel, bool vibrato);
 	void WriteValue(uint32_t regbase, uint32_t channel, uint8_t value);
 	void WriteFrequency(uint32_t channel, uint32_t freq, uint32_t octave, uint32_t keyon);
-	void WriteVolume(uint32_t channel, genmidi_voice_t *voice, uint32_t v1, uint32_t v2, uint32_t v3);
-	void WritePan(uint32_t channel, genmidi_voice_t *voice, int pan);
-	void WriteTremolo(uint32_t channel, genmidi_voice_t *voice, bool vibrato);
-	void WriteInstrument(uint32_t channel, genmidi_voice_t *voice, bool vibrato);
+	void WriteVolume(uint32_t channel, GenMidiVoice *voice, uint32_t v1, uint32_t v2, uint32_t v3);
+	void WritePan(uint32_t channel, GenMidiVoice *voice, int pan);
+	void WriteTremolo(uint32_t channel, GenMidiVoice *voice, bool vibrato);
+	void WriteInstrument(uint32_t channel, GenMidiVoice *voice, bool vibrato);
 	void WriteInitState(bool opl3);
 	void MuteChannel(uint32_t chan);
 	void StopPlayback();