diff --git a/papers/doc/7-systems/opz.md b/papers/doc/7-systems/opz.md
index dd69c85c..c7812740 100644
--- a/papers/doc/7-systems/opz.md
+++ b/papers/doc/7-systems/opz.md
@@ -46,10 +46,10 @@ no plans have been made for TX81Z MIDI passthrough, because:
 - `28xy`: set reverb of operator.
   - `x` is the operator (1-4). a value of 0 means "all operators".
   - `y` is the value.
-- `29xy`: set EG shift of operator.
+- `2Axy`: set waveform of operator.
   - `x` is the operator (1-4). a value of 0 means "all operators".
   - `y` is the value.
-- `2Axy`: set waveform of operator.
+- `2Bxy`: set EG shift of operator.
   - `x` is the operator (1-4). a value of 0 means "all operators".
   - `y` is the value.
 - `2Fxx`: enable envelope hard reset.
diff --git a/src/engine/dispatch.h b/src/engine/dispatch.h
index 9b906220..d212b090 100644
--- a/src/engine/dispatch.h
+++ b/src/engine/dispatch.h
@@ -78,6 +78,8 @@ enum DivDispatchCmds {
   DIV_CMD_FM_SUS, // (op, value)
   DIV_CMD_FM_WS, // (op, value)
   DIV_CMD_FM_SSG, // (op, value)
+  DIV_CMD_FM_REV, // (op, value)
+  DIV_CMD_FM_EG_SHIFT, // (op, value)
   DIV_CMD_FM_FB, // (value)
   DIV_CMD_FM_MULT, // (op, value)
   DIV_CMD_FM_FINE, // (op, value)
diff --git a/src/engine/engine.h b/src/engine/engine.h
index 2669dddb..0c1e07a7 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -45,8 +45,8 @@
 #define BUSY_BEGIN_SOFT softLocked=true; isBusy.lock();
 #define BUSY_END isBusy.unlock(); softLocked=false;
 
-#define DIV_VERSION "dev90"
-#define DIV_ENGINE_VERSION 90
+#define DIV_VERSION "dev91"
+#define DIV_ENGINE_VERSION 91
 
 // for imports
 #define DIV_VERSION_MOD 0xff01
diff --git a/src/engine/platform/ay8930.cpp b/src/engine/platform/ay8930.cpp
index 5b823606..3fec732b 100644
--- a/src/engine/platform/ay8930.cpp
+++ b/src/engine/platform/ay8930.cpp
@@ -27,7 +27,7 @@
 #define rWrite(a,v) if (!skipRegisterWrites) {pendingWrites[a]=v;}
 #define immWrite2(a,v) if (!skipRegisterWrites) {writes.emplace(a,v); if (dumpWrites) {addWrite(a,v);} }
 
-#define CHIP_DIVIDER 8
+#define CHIP_DIVIDER 4
 
 const char* regCheatSheetAY8930[]={
   "FreqL_A", "00",
@@ -645,7 +645,7 @@ void DivPlatformAY8930::setFlags(unsigned int flags) {
       chipClock=COLOR_NTSC/2.0;
       break;
   }
-  rate=chipClock/8;
+  rate=chipClock/4;
   for (int i=0; i<3; i++) {
     oscBuf[i]->rate=rate;
   }
diff --git a/src/engine/platform/opl.cpp b/src/engine/platform/opl.cpp
index dfe83d36..dc121a06 100644
--- a/src/engine/platform/opl.cpp
+++ b/src/engine/platform/opl.cpp
@@ -940,6 +940,7 @@ void* DivPlatformOPL::getChanState(int ch) {
 }
 
 DivDispatchOscBuffer* DivPlatformOPL::getOscBuffer(int ch) {
+  if (ch>=18) return NULL;
   return oscBuf[ch];
 }
 
diff --git a/src/engine/platform/sound/ay8910.cpp b/src/engine/platform/sound/ay8910.cpp
index 8bb38788..4d19e7de 100644
--- a/src/engine/platform/sound/ay8910.cpp
+++ b/src/engine/platform/sound/ay8910.cpp
@@ -1064,7 +1064,7 @@ void ay8910_device::sound_stream_update(short** outputs, int outLen)
 		{
 			tone = &m_tone[chan];
 			const int period = std::max<int>(1,tone->period);
-			tone->count += is_expanded_mode() ? 16 : 1;
+			tone->count += is_expanded_mode() ? 16 : (m_feature & PSG_HAS_EXPANDED_MODE) ? 2 : 1;
 			while (tone->count >= period)
 			{
 				tone->duty_cycle = (tone->duty_cycle - 1) & 0x1f;
@@ -1080,7 +1080,7 @@ void ay8910_device::sound_stream_update(short** outputs, int outLen)
 			 * channels.
 			 */
 			m_count_noise = 0;
-			m_prescale_noise ^= 1;
+			m_prescale_noise = (m_prescale_noise + 1) & ((m_feature & PSG_HAS_EXPANDED_MODE) ? 3 : 1);
 
 			if (!m_prescale_noise || is_expanded_mode()) // AY8930 noise generator rate is twice compares as compatibility mode
 			{
@@ -1469,7 +1469,7 @@ ay8910_device::ay8910_device(device_type type, unsigned int clock,
     m_noise_latch(0),
 		m_mode(0),
 		m_env_step_mask((!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? 0x0f : 0x1f),
-		m_step(         (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? 2 : 1),
+		m_step(         (feature & PSG_HAS_EXPANDED_MODE) || (psg_type == PSG_TYPE_AY) ? 2 : 1),
 		m_zero_is_off(  (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? 1 : 0),
 		m_par(          (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? &ay8910_param : &ym2149_param),
 		m_par_env(      (!(feature & PSG_HAS_EXPANDED_MODE)) && (psg_type == PSG_TYPE_AY) ? &ay8910_param : &ym2149_param_env),
@@ -1502,7 +1502,7 @@ void ay8910_device::set_type(psg_type_t psg_type)
 	else
 	{
 		m_env_step_mask = 0x1f;
-		m_step = 1;
+		m_step = (m_feature & PSG_HAS_EXPANDED_MODE) ? 2 : 1;
 		m_zero_is_off = 0;
 		m_par = &ym2149_param;
 		m_par_env = &ym2149_param_env;
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index 4cb224ed..496a0434 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -80,6 +80,8 @@ const char* cmdName[]={
   "FM_SUS",
   "FM_WS",
   "FM_SSG",
+  "FM_REV",
+  "FM_EG_SHIFT",
   "FM_FB",
   "FM_MULT",
   "FM_FINE",
diff --git a/src/engine/sample.cpp b/src/engine/sample.cpp
index fcbc370c..007a4e17 100644
--- a/src/engine/sample.cpp
+++ b/src/engine/sample.cpp
@@ -75,7 +75,7 @@ bool DivSample::save(const char* path) {
   }
   sf_command(f, SFC_SET_INSTRUMENT, &inst, sizeof(inst));
 
-  sf_write_short(f,data16,length16);
+  sf_writef_short(f,data16,samples);
 
   sf_close(f);
 
diff --git a/src/engine/sysDef.cpp b/src/engine/sysDef.cpp
index 36331f70..405f39d9 100644
--- a/src/engine/sysDef.cpp
+++ b/src/engine/sysDef.cpp
@@ -319,6 +319,18 @@ int DivEngine::minVGMVersion(DivSystem which) {
 #define IS_YM2610 (sysOfChan[ch]==DIV_SYSTEM_YM2610 || sysOfChan[ch]==DIV_SYSTEM_YM2610_EXT || sysOfChan[ch]==DIV_SYSTEM_YM2610_FULL || sysOfChan[ch]==DIV_SYSTEM_YM2610_FULL_EXT || sysOfChan[ch]==DIV_SYSTEM_YM2610B || sysOfChan[ch]==DIV_SYSTEM_YM2610B_EXT)
 #define IS_OPM_LIKE (sysOfChan[ch]==DIV_SYSTEM_YM2151 || sysOfChan[ch]==DIV_SYSTEM_OPZ)
 
+#define OP_EFFECT_MULTI(x,c,op,mask) \
+  case x: \
+    dispatchCmd(DivCommand(c,ch,op,effectVal&mask)); \
+    break;
+
+#define OP_EFFECT_SINGLE(x,c,maxOp,mask) \
+  case x: \
+    if ((effectVal>>4)>=0 && (effectVal>>4)<=maxOp) { \
+      dispatchCmd(DivCommand(c,ch,(effectVal>>4)-1,effectVal&mask)); \
+    } \
+    break;
+
 // define systems like:
 // sysDefs[DIV_SYSTEM_ID]=new DivSysDef(
 //   "Name", "Name (japanese, optional)", fileID, fileID_DMF, channels, isFM, isSTD, vgmVersion,
@@ -436,6 +448,54 @@ void DivEngine::registerSystems() {
           dispatchCmd(DivCommand(DIV_CMD_AY_AUTO_ENVELOPE,ch,effectVal));
         }
         break;
+      // fixed frequency effects on OPZ
+      case 0x30: case 0x31: case 0x32: case 0x33:
+      case 0x34: case 0x35: case 0x36: case 0x37:
+        if (sysOfChan[ch]==DIV_SYSTEM_OPZ) {
+          dispatchCmd(DivCommand(DIV_CMD_FM_FIXFREQ,ch,0,((effect&7)<<8)|effectVal));
+        }
+        break;
+      case 0x38: case 0x39: case 0x3a: case 0x3b:
+      case 0x3c: case 0x3d: case 0x3e: case 0x3f:
+        if (sysOfChan[ch]==DIV_SYSTEM_OPZ) {
+          dispatchCmd(DivCommand(DIV_CMD_FM_FIXFREQ,ch,1,((effect&7)<<8)|effectVal));
+        }
+        break;
+      case 0x40: case 0x41: case 0x42: case 0x43:
+      case 0x44: case 0x45: case 0x46: case 0x47:
+        if (sysOfChan[ch]==DIV_SYSTEM_OPZ) {
+          dispatchCmd(DivCommand(DIV_CMD_FM_FIXFREQ,ch,2,((effect&7)<<8)|effectVal));
+        }
+        break;
+      case 0x48: case 0x49: case 0x4a: case 0x4b:
+      case 0x4c: case 0x4d: case 0x4e: case 0x4f:
+        if (sysOfChan[ch]==DIV_SYSTEM_OPZ) {
+          dispatchCmd(DivCommand(DIV_CMD_FM_FIXFREQ,ch,3,((effect&7)<<8)|effectVal));
+        }
+        break;
+      // extra FM effects here
+      OP_EFFECT_SINGLE(0x50,DIV_CMD_FM_AM,4,1);
+      OP_EFFECT_SINGLE(0x51,DIV_CMD_FM_SL,4,15);
+      OP_EFFECT_SINGLE(0x52,DIV_CMD_FM_RR,4,15);
+      OP_EFFECT_SINGLE(0x53,DIV_CMD_FM_DT,4,7);
+      OP_EFFECT_SINGLE(0x54,DIV_CMD_FM_RS,4,3);
+      OP_EFFECT_SINGLE(0x55,DIV_CMD_FM_SSG,4,(IS_OPM_LIKE?3:15));
+
+      OP_EFFECT_MULTI(0x56,DIV_CMD_FM_DR,-1,31);
+      OP_EFFECT_MULTI(0x57,DIV_CMD_FM_DR,0,31);
+      OP_EFFECT_MULTI(0x58,DIV_CMD_FM_DR,1,31);
+      OP_EFFECT_MULTI(0x59,DIV_CMD_FM_DR,2,31);
+      OP_EFFECT_MULTI(0x5a,DIV_CMD_FM_DR,3,31);
+
+      OP_EFFECT_MULTI(0x5b,DIV_CMD_FM_D2R,-1,31);
+      OP_EFFECT_MULTI(0x5c,DIV_CMD_FM_D2R,0,31);
+      OP_EFFECT_MULTI(0x5d,DIV_CMD_FM_D2R,1,31);
+      OP_EFFECT_MULTI(0x5e,DIV_CMD_FM_D2R,2,31);
+      OP_EFFECT_MULTI(0x5f,DIV_CMD_FM_D2R,3,31);
+
+      OP_EFFECT_SINGLE(0x28,DIV_CMD_FM_REV,4,7);
+      OP_EFFECT_SINGLE(0x2a,DIV_CMD_FM_WS,4,7);
+      OP_EFFECT_SINGLE(0x2b,DIV_CMD_FM_EG_SHIFT,4,3);
       default:
         return false;
     }
@@ -467,6 +527,21 @@ void DivEngine::registerSystems() {
       case 0x1b: // AR op2
         dispatchCmd(DivCommand(DIV_CMD_FM_AR,ch,1,effectVal&31));
         break;
+
+      // extra FM effects here
+      OP_EFFECT_SINGLE(0x50,DIV_CMD_FM_AM,2,1);
+      OP_EFFECT_SINGLE(0x51,DIV_CMD_FM_SL,2,15);
+      OP_EFFECT_SINGLE(0x52,DIV_CMD_FM_RR,2,15);
+      OP_EFFECT_SINGLE(0x53,DIV_CMD_FM_VIB,2,1);
+      OP_EFFECT_SINGLE(0x54,DIV_CMD_FM_RS,2,3);
+      OP_EFFECT_SINGLE(0x55,DIV_CMD_FM_SUS,2,1);
+
+      OP_EFFECT_MULTI(0x56,DIV_CMD_FM_DR,-1,15);
+      OP_EFFECT_MULTI(0x57,DIV_CMD_FM_DR,0,15);
+      OP_EFFECT_MULTI(0x58,DIV_CMD_FM_DR,1,15);
+
+      OP_EFFECT_SINGLE(0x5b,DIV_CMD_FM_KSR,2,1);
+      OP_EFFECT_SINGLE(0x2a,DIV_CMD_FM_WS,4,7);
       default:
         return false;
     }
@@ -516,6 +591,23 @@ void DivEngine::registerSystems() {
       case 0x1d: // AR op4
         dispatchCmd(DivCommand(DIV_CMD_FM_AR,ch,3,effectVal&15));
         break;
+      
+      // extra FM effects here
+      OP_EFFECT_SINGLE(0x50,DIV_CMD_FM_AM,4,1);
+      OP_EFFECT_SINGLE(0x51,DIV_CMD_FM_SL,4,15);
+      OP_EFFECT_SINGLE(0x52,DIV_CMD_FM_RR,4,15);
+      OP_EFFECT_SINGLE(0x53,DIV_CMD_FM_VIB,4,1);
+      OP_EFFECT_SINGLE(0x54,DIV_CMD_FM_RS,4,3);
+      OP_EFFECT_SINGLE(0x55,DIV_CMD_FM_SUS,4,1);
+
+      OP_EFFECT_MULTI(0x56,DIV_CMD_FM_DR,-1,15);
+      OP_EFFECT_MULTI(0x57,DIV_CMD_FM_DR,0,15);
+      OP_EFFECT_MULTI(0x58,DIV_CMD_FM_DR,1,15);
+      OP_EFFECT_MULTI(0x59,DIV_CMD_FM_DR,2,15);
+      OP_EFFECT_MULTI(0x5a,DIV_CMD_FM_DR,3,15);
+
+      OP_EFFECT_SINGLE(0x5b,DIV_CMD_FM_KSR,4,1);
+
       default:
         return false;
     }