diff --git a/CMakeLists.txt b/CMakeLists.txt
index 549f5d79..906bacff 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -530,6 +530,7 @@ src/engine/platform/t6w28.cpp
 src/engine/platform/vb.cpp
 src/engine/platform/vera.cpp
 src/engine/platform/zxbeeper.cpp
+src/engine/platform/zxbeeperquadtone.cpp
 src/engine/platform/bubsyswsg.cpp
 src/engine/platform/n163.cpp
 src/engine/platform/pet.cpp
diff --git a/src/engine/dispatchContainer.cpp b/src/engine/dispatchContainer.cpp
index de37948f..c30d7f23 100644
--- a/src/engine/dispatchContainer.cpp
+++ b/src/engine/dispatchContainer.cpp
@@ -59,6 +59,7 @@
 #include "platform/lynx.h"
 #include "platform/pokey.h"
 #include "platform/zxbeeper.h"
+#include "platform/zxbeeperquadtone.h"
 #include "platform/bubsyswsg.h"
 #include "platform/n163.h"
 #include "platform/pet.h"
@@ -389,6 +390,9 @@ void DivDispatchContainer::init(DivSystem sys, DivEngine* eng, int chanCount, do
     case DIV_SYSTEM_SFX_BEEPER:
       dispatch=new DivPlatformZXBeeper;
       break;
+    case DIV_SYSTEM_SFX_BEEPER_QUADTONE:
+      dispatch=new DivPlatformZXBeeperQuadTone;
+      break;
     case DIV_SYSTEM_LYNX:
       dispatch=new DivPlatformLynx;
       break;
diff --git a/src/engine/fileOps.cpp b/src/engine/fileOps.cpp
index d7605269..c679019a 100644
--- a/src/engine/fileOps.cpp
+++ b/src/engine/fileOps.cpp
@@ -1479,6 +1479,7 @@ void DivEngine::convertOldFlags(unsigned int oldFlags, DivConfig& newFlags, DivS
       }
       break;
     case DIV_SYSTEM_SFX_BEEPER:
+    case DIV_SYSTEM_SFX_BEEPER_QUADTONE:
       newFlags.set("clockSel",(int)(oldFlags&1));
       break;
     case DIV_SYSTEM_SCC:
diff --git a/src/engine/platform/zxbeeperquadtone.cpp b/src/engine/platform/zxbeeperquadtone.cpp
new file mode 100644
index 00000000..50082d04
--- /dev/null
+++ b/src/engine/platform/zxbeeperquadtone.cpp
@@ -0,0 +1,389 @@
+/**
+ * Furnace Tracker - multi-system chiptune tracker
+ * Copyright (C) 2021-2022 tildearrow and contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "zxbeeperquadtone.h"
+#include "../engine.h"
+#include <math.h>
+
+#define rWrite(a,v) regPool[a]=v
+#define CHIP_FREQBASE 2048*320
+#define CHIP_DIVIDER 16*13
+
+const char** DivPlatformZXBeeperQuadTone::getRegisterSheet() {
+  return NULL;
+}
+
+void DivPlatformZXBeeperQuadTone::acquire(short** buf, size_t len) {
+  bool o=false;
+  for (size_t h=0; h<len; h++) {
+    if (curSample>=0 && curSample<parent->song.sampleLen) {
+      while (curSamplePeriod>=chan[4].freq) {
+        DivSample* s=parent->getSample(curSample);
+        if (s->samples>0) {
+          o=(!isMuted[4]&&s->data8[curSamplePos++]>0);
+          if (curSamplePos>=s->samples) curSample=-1;
+          // (theoretical) 32KiB limit
+          if (curSamplePos>=32768*8) curSample=-1;
+        } else {
+          curSample=-1;
+        }
+        curSamplePeriod-=chan[4].freq;
+      }
+      curSamplePeriod+=40;
+      if ((outputClock&3)==0) {
+        oscBuf[0]->data[oscBuf[0]->needle++]=0;
+        oscBuf[1]->data[oscBuf[1]->needle++]=0;
+        oscBuf[2]->data[oscBuf[2]->needle++]=0;
+        oscBuf[3]->data[oscBuf[3]->needle++]=0;
+        oscBuf[4]->data[oscBuf[4]->needle++]=o?32767:0;
+      }
+    } else {
+      int ch=outputClock/2;
+      int b=ch*4;
+      if ((outputClock&1)==0) {
+        chan[ch].sPosition+=(regPool[1+b]<<8)|regPool[0+b];
+        chan[ch].out=regPool[3+b]+((((chan[ch].sPosition>>8)&0xff)<regPool[2+b])?1:0);
+      }
+      if ((outputClock&3)==0) {
+        oscBuf[4]->data[oscBuf[4]->needle++]=0;
+      }
+      o=chan[ch].out&0x10;
+      oscBuf[ch]->data[oscBuf[ch]->needle++]=o?32767:0;
+      chan[ch].out<<=1;
+    }
+    outputClock=(outputClock+1)&7;
+    buf[0][h]=o?32767:0;
+  }
+}
+
+void DivPlatformZXBeeperQuadTone::tick(bool sysTick) {
+  for (int i=0; i<4; i++) {
+    chan[i].std.next();
+    if (chan[i].std.vol.had) {
+      chan[i].outVol=(MIN(chan[i].vol,2)*MIN(chan[i].std.vol.val,2)/2);
+      writeOutVol(i);
+    }
+    if (chan[i].std.duty.had) {
+      chan[i].duty=chan[i].std.duty.val;
+      rWrite(2+i*4,chan[i].duty^0xff);
+    }
+    if (NEW_ARP_STRAT) {
+      chan[i].handleArp();
+    } else if (chan[i].std.arp.had) {
+      if (!chan[i].inPorta) {
+        chan[i].baseFreq=NOTE_FREQUENCY(parent->calcArp(chan[i].note,chan[i].std.arp.val));
+      }
+      chan[i].freqChanged=true;
+    }
+    if (chan[i].std.pitch.had) {
+      if (chan[i].std.pitch.mode) {
+        chan[i].pitch2+=chan[i].std.pitch.val;
+        CLAMP_VAR(chan[i].pitch2,-65535,65535);
+      } else {
+        chan[i].pitch2=chan[i].std.pitch.val;
+      }
+      chan[i].freqChanged=true;
+    }
+    if (chan[i].freqChanged || chan[i].keyOn || chan[i].keyOff) {
+      if (chan[i].active) {
+        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,chan[i].fixedArp?chan[i].baseNoteOverride:chan[i].arpOff,chan[i].fixedArp,false,2,chan[i].pitch2,chipClock,CHIP_FREQBASE);
+        if (chan[i].freq<0) chan[i].freq=0;
+        if (chan[i].freq>32768) chan[i].freq=32768;
+        rWrite(0+i*4,chan[i].freq&0xff);
+        rWrite(1+i*4,chan[i].freq>>8);
+      }
+      if (chan[i].keyOn) chan[i].keyOn=false;
+      if (chan[i].keyOff) chan[i].keyOff=false;
+      chan[i].freqChanged=false;
+    }
+  }
+  if (NEW_ARP_STRAT) {
+    chan[4].handleArp();
+  } else if (chan[4].std.arp.had) {
+    if (!chan[4].inPorta) {
+      chan[4].baseFreq=NOTE_PERIODIC(parent->calcArp(chan[4].note,chan[4].std.arp.val));
+    }
+    chan[4].freqChanged=true;
+  }
+  if (chan[4].std.pitch.had) {
+    if (chan[4].std.pitch.mode) {
+      chan[4].pitch2+=chan[4].std.pitch.val;
+      CLAMP_VAR(chan[4].pitch2,-65535,65535);
+    } else {
+      chan[4].pitch2=chan[4].std.pitch.val;
+    }
+    chan[4].freqChanged=true;
+  }
+  if (chan[4].freqChanged || chan[4].keyOn || chan[4].keyOff) {
+    if (chan[4].active) {
+      double off=CHIP_DIVIDER;
+      if (curSample>=0 && curSample<parent->song.sampleLen) {
+        DivSample* s=parent->getSample(curSample);
+        off=(s->centerRate>=1)?(CHIP_DIVIDER*(double)s->centerRate/8363.0):CHIP_DIVIDER;
+      }
+      chan[4].freq=parent->calcFreq(chan[4].baseFreq,chan[4].pitch,chan[4].fixedArp?chan[4].baseNoteOverride:chan[4].arpOff,chan[4].fixedArp,true,2,chan[4].pitch2,chipClock,off);
+      if (chan[4].freq>258) chan[4].freq=258;
+      if (chan[4].freq<3) chan[4].freq=3;
+      chan[4].freq*=13;
+    }
+    if (chan[4].keyOn) chan[4].keyOn=false;
+    if (chan[4].keyOff) chan[4].keyOff=false;
+    chan[4].freqChanged=false;
+  }
+}
+
+int DivPlatformZXBeeperQuadTone::dispatch(DivCommand c) {
+  switch (c.cmd) {
+    case DIV_CMD_NOTE_ON: {
+      if (c.chan<4) {
+        DivInstrument* ins=parent->getIns(chan[c.chan].ins,DIV_INS_BEEPER);
+        if (c.value!=DIV_NOTE_NULL) {
+          chan[c.chan].baseFreq=NOTE_FREQUENCY(c.value);
+          chan[c.chan].freqChanged=true;
+          chan[c.chan].note=c.value;
+        }
+        chan[c.chan].active=true;
+        chan[c.chan].keyOn=true;
+        chan[c.chan].macroInit(ins);
+        chan[c.chan].insChanged=false;
+        if (!parent->song.brokenOutVol && !chan[c.chan].std.vol.will) {
+          chan[c.chan].outVol=chan[c.chan].vol;
+          writeOutVol(c.chan);
+        }
+      } else {
+        DivInstrument* ins=parent->getIns(chan[c.chan].ins,DIV_INS_AMIGA);
+        if (c.value!=DIV_NOTE_NULL) {
+          chan[c.chan].baseFreq=NOTE_PERIODIC(c.value);
+          chan[c.chan].freqChanged=true;
+          chan[c.chan].note=c.value;
+          curSample=ins->amiga.getSample(c.value);
+          // TODO support offset commands
+          curSamplePos=0;
+          curSamplePeriod=0;
+        }
+        chan[c.chan].active=true;
+        chan[c.chan].keyOn=true;
+        chan[c.chan].macroInit(ins);
+        chan[c.chan].insChanged=false;
+      }
+      break;
+    }
+    case DIV_CMD_NOTE_OFF:
+      chan[c.chan].active=false;
+      chan[c.chan].keyOff=true;
+      chan[c.chan].macroInit(NULL);
+      writeOutVol(c.chan);
+      if (c.chan>=4) {
+        curSample=-1;
+      }
+      break;
+    case DIV_CMD_NOTE_OFF_ENV:
+    case DIV_CMD_ENV_RELEASE:
+      chan[c.chan].std.release();
+      break;
+    case DIV_CMD_INSTRUMENT:
+      if (chan[c.chan].ins!=c.value || c.value2==1) {
+        chan[c.chan].ins=c.value;
+        chan[c.chan].insChanged=true;
+      }
+      break;
+    case DIV_CMD_VOLUME:
+      if (chan[c.chan].vol!=c.value) {
+        chan[c.chan].vol=c.value;
+        if (!chan[c.chan].std.vol.has) {
+          chan[c.chan].outVol=c.value;
+          writeOutVol(c.chan);
+        }
+      }
+      break;
+    case DIV_CMD_GET_VOLUME:
+      if (chan[c.chan].std.vol.has) {
+        return chan[c.chan].vol;
+      }
+      return chan[c.chan].outVol;
+      break;
+    case DIV_CMD_PITCH:
+      chan[c.chan].pitch=c.value;
+      chan[c.chan].freqChanged=true;
+      break;
+    case DIV_CMD_NOTE_PORTA: {
+      int destFreq=NOTE_FREQUENCY(c.value2);
+      bool return2=false;
+      if (destFreq>chan[c.chan].baseFreq) {
+        chan[c.chan].baseFreq+=c.value;
+        if (chan[c.chan].baseFreq>=destFreq) {
+          chan[c.chan].baseFreq=destFreq;
+          return2=true;
+        }
+      } else {
+        chan[c.chan].baseFreq-=c.value;
+        if (chan[c.chan].baseFreq<=destFreq) {
+          chan[c.chan].baseFreq=destFreq;
+          return2=true;
+        }
+      }
+      chan[c.chan].freqChanged=true;
+      if (return2) {
+        chan[c.chan].inPorta=false;
+        return 2;
+      }
+      break;
+    }
+    case DIV_CMD_STD_NOISE_MODE:
+      chan[c.chan].duty=c.value;
+      if (c.chan<4) rWrite(2+c.chan*4,chan[c.chan].duty^0xff);
+      break;
+    case DIV_CMD_LEGATO:
+      chan[c.chan].baseFreq=NOTE_FREQUENCY(c.value+((HACKY_LEGATO_MESS)?(chan[c.chan].std.arp.val):(0)));
+      chan[c.chan].freqChanged=true;
+      chan[c.chan].note=c.value;
+      break;
+    case DIV_CMD_PRE_PORTA:
+      if (chan[c.chan].active && c.value2) {
+        if (parent->song.resetMacroOnPorta) chan[c.chan].macroInit(parent->getIns(chan[c.chan].ins,DIV_INS_BEEPER));
+      }
+      if (!chan[c.chan].inPorta && c.value && !parent->song.brokenPortaArp && chan[c.chan].std.arp.will && !NEW_ARP_STRAT) chan[c.chan].baseFreq=NOTE_FREQUENCY(chan[c.chan].note);
+      chan[c.chan].inPorta=c.value;
+      break;
+    case DIV_CMD_GET_VOLMAX:
+      return 2;
+      break;
+    case DIV_CMD_MACRO_OFF:
+      chan[c.chan].std.mask(c.value,true);
+      break;
+    case DIV_CMD_MACRO_ON:
+      chan[c.chan].std.mask(c.value,false);
+      break;
+    case DIV_ALWAYS_SET_VOLUME:
+      return 1;
+      break;
+    default:
+      break;
+  }
+  return 1;
+}
+
+void DivPlatformZXBeeperQuadTone::writeOutVol(int ch) {
+  if (ch>=4) return;
+  unsigned char val=(chan[ch].outVol>=1)?((chan[ch].outVol>=2)?31:7):0;
+  rWrite(3+ch*4,(!isMuted[ch]&&chan[ch].active)?val:0);
+}
+
+void DivPlatformZXBeeperQuadTone::muteChannel(int ch, bool mute) {
+  isMuted[ch]=mute;
+  writeOutVol(ch);
+}
+
+void DivPlatformZXBeeperQuadTone::forceIns() {
+  for (int i=0; i<5; i++) {
+    chan[i].insChanged=true;
+    chan[i].freqChanged=true;
+  }
+}
+
+void* DivPlatformZXBeeperQuadTone::getChanState(int ch) {
+  return &chan[ch];
+}
+
+DivMacroInt* DivPlatformZXBeeperQuadTone::getChanMacroInt(int ch) {
+  return &chan[ch].std;
+}
+
+DivDispatchOscBuffer* DivPlatformZXBeeperQuadTone::getOscBuffer(int ch) {
+  return oscBuf[ch];
+}
+
+unsigned char* DivPlatformZXBeeperQuadTone::getRegisterPool() {
+  return regPool;
+}
+
+int DivPlatformZXBeeperQuadTone::getRegisterPoolSize() {
+  return 16;
+}
+
+void DivPlatformZXBeeperQuadTone::reset() {
+  memset(regPool,0,16);
+  for (int i=0; i<5; i++) {
+    chan[i]=DivPlatformZXBeeperQuadTone::Channel();
+    chan[i].std.setEngine(parent);
+    if (i<4) rWrite(2+i*4,128);
+  }
+  cycles=0;
+  curChan=0;
+  sOffTimer=0;
+  ulaOut=0;
+  curSample=-1;
+  curSamplePos=0;
+  curSamplePeriod=0;
+  outputClock=0;
+}
+
+bool DivPlatformZXBeeperQuadTone::keyOffAffectsArp(int ch) {
+  return true;
+}
+
+void DivPlatformZXBeeperQuadTone::notifyWaveChange(int wave) {
+}
+
+void DivPlatformZXBeeperQuadTone::notifyInsDeletion(void* ins) {
+  for (int i=0; i<5; i++) {
+    chan[i].std.notifyInsDeletion((DivInstrument*)ins);
+  }
+}
+
+void DivPlatformZXBeeperQuadTone::setFlags(const DivConfig& flags) {
+  if (flags.getInt("clockSel",0)) {
+    chipClock=COLOR_PAL*4.0/5.0;
+  } else {
+    chipClock=COLOR_NTSC;
+  }
+  CHECK_CUSTOM_CLOCK;
+  rate=chipClock/40;
+  for (int i=0; i<4; i++) {
+    oscBuf[i]->rate=rate/4;
+  }
+}
+
+void DivPlatformZXBeeperQuadTone::poke(unsigned int addr, unsigned short val) {
+  rWrite(addr,val);
+}
+
+void DivPlatformZXBeeperQuadTone::poke(std::vector<DivRegWrite>& wlist) {
+  for (DivRegWrite& i: wlist) rWrite(i.addr,i.val);
+}
+
+int DivPlatformZXBeeperQuadTone::init(DivEngine* p, int channels, int sugRate, const DivConfig& flags) {
+  parent=p;
+  for (int i=0; i<5; i++) {
+    isMuted[i]=false;
+    oscBuf[i]=new DivDispatchOscBuffer;
+  }
+  setFlags(flags);
+  reset();
+  return 5;
+}
+
+void DivPlatformZXBeeperQuadTone::quit() {
+  for (int i=0; i<5; i++) {
+    delete oscBuf[i];
+  }
+}
+
+DivPlatformZXBeeperQuadTone::~DivPlatformZXBeeperQuadTone() {
+}
diff --git a/src/engine/platform/zxbeeperquadtone.h b/src/engine/platform/zxbeeperquadtone.h
new file mode 100644
index 00000000..7da58b1d
--- /dev/null
+++ b/src/engine/platform/zxbeeperquadtone.h
@@ -0,0 +1,73 @@
+/**
+ * Furnace Tracker - multi-system chiptune tracker
+ * Copyright (C) 2021-2022 tildearrow and contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef _ZXBEEPERQUADTONE_H
+#define _ZXBEEPERQUADTONE_H
+
+#include "../dispatch.h"
+
+class DivPlatformZXBeeperQuadTone: public DivDispatch {
+  struct Channel: public SharedChannel<unsigned char> {
+    unsigned short sPosition;
+    unsigned char duty;
+    unsigned char out;
+    Channel():
+      SharedChannel<unsigned char>(2),
+      sPosition(0),
+      duty(128),
+      out(0) {}
+  };
+  Channel chan[5];
+  DivDispatchOscBuffer* oscBuf[5];
+  bool isMuted[5];
+  unsigned char ulaOut;
+
+  int cycles, curChan, sOffTimer, delay, curSample, curSamplePeriod;
+  unsigned int curSamplePos;
+  unsigned int outputClock;
+  unsigned char regPool[16];
+  friend void putDispatchChip(void*,int);
+  friend void putDispatchChan(void*,int,int);
+  public:
+    void acquire(short** buf, size_t len);
+    int dispatch(DivCommand c);
+    void* getChanState(int chan);
+    DivMacroInt* getChanMacroInt(int ch);
+    DivDispatchOscBuffer* getOscBuffer(int chan);
+    unsigned char* getRegisterPool();
+    int getRegisterPoolSize();
+    void reset();
+    void forceIns();
+    void tick(bool sysTick=true);
+    void muteChannel(int ch, bool mute);
+    bool keyOffAffectsArp(int ch);
+    void setFlags(const DivConfig& flags);
+    void notifyWaveChange(int wave);
+    void notifyInsDeletion(void* ins);
+    void poke(unsigned int addr, unsigned short val);
+    void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
+    int init(DivEngine* parent, int channels, int sugRate, const DivConfig& flags);
+    void quit();
+    ~DivPlatformZXBeeperQuadTone();
+  private:
+    void writeOutVol(int ch);
+};
+
+#endif
diff --git a/src/engine/song.h b/src/engine/song.h
index cfed6b4c..cb838f24 100644
--- a/src/engine/song.h
+++ b/src/engine/song.h
@@ -83,6 +83,7 @@ enum DivSystem {
   DIV_SYSTEM_VRC7,
   DIV_SYSTEM_YM2610B,
   DIV_SYSTEM_SFX_BEEPER,
+  DIV_SYSTEM_SFX_BEEPER_QUADTONE,
   DIV_SYSTEM_YM2612_EXT,
   DIV_SYSTEM_SCC,
   DIV_SYSTEM_OPL_DRUMS,
diff --git a/src/engine/sysDef.cpp b/src/engine/sysDef.cpp
index 3bf5da5e..509dc02c 100644
--- a/src/engine/sysDef.cpp
+++ b/src/engine/sysDef.cpp
@@ -1842,6 +1842,19 @@ void DivEngine::registerSystems() {
     {DIV_INS_PV1000, DIV_INS_PV1000, DIV_INS_PV1000}
   );
 
+  sysDefs[DIV_SYSTEM_SFX_BEEPER_QUADTONE]=new DivSysDef(
+    "ZX Spectrum Beeper (QuadTone Engine)", NULL, 0xca, 0, 5, false, true, 0, false, 1U<<DIV_SAMPLE_DEPTH_8BIT,
+    "Another ZX Spectrum beeper system with full PWM pulses and 3-level volume per channel. It also has a pitchable overlay sample channel.",
+    {"Channel 1", "Channel 2", "Channel 3", "Channel 4", "PCM"},
+    {"CH1", "CH2", "CH3", "CH4", "PCM"},
+    {DIV_CH_PULSE, DIV_CH_PULSE, DIV_CH_PULSE, DIV_CH_PULSE, DIV_CH_PCM},
+    {DIV_INS_BEEPER, DIV_INS_BEEPER, DIV_INS_BEEPER, DIV_INS_BEEPER, DIV_INS_AMIGA},
+    {},
+    {
+      {0x12, {DIV_CMD_STD_NOISE_MODE, "12xx: Set pulse width"}}
+    }
+  );
+
   sysDefs[DIV_SYSTEM_DUMMY]=new DivSysDef(
     "Dummy System", NULL, 0xfd, 0, 8, false, true, 0, false, 0,
     "this is a system designed for testing purposes.",
diff --git a/src/gui/guiConst.cpp b/src/gui/guiConst.cpp
index 790e8547..07f959ad 100644
--- a/src/gui/guiConst.cpp
+++ b/src/gui/guiConst.cpp
@@ -952,6 +952,7 @@ const int availableSystems[]={
   DIV_SYSTEM_PCSPKR,
   DIV_SYSTEM_POKEMINI,
   DIV_SYSTEM_SFX_BEEPER,
+  DIV_SYSTEM_SFX_BEEPER_QUADTONE,
   DIV_SYSTEM_YMU759,
   DIV_SYSTEM_DUMMY,
   DIV_SYSTEM_SOUND_UNIT,
@@ -1081,6 +1082,7 @@ const int chipsSpecial[]={
   DIV_SYSTEM_C64_8580,
   DIV_SYSTEM_C64_6581,
   DIV_SYSTEM_SFX_BEEPER,
+  DIV_SYSTEM_SFX_BEEPER_QUADTONE,
   DIV_SYSTEM_DUMMY,
   DIV_SYSTEM_SOUND_UNIT,
   DIV_SYSTEM_TIA,