diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index d48c57f37..14955140e 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -4748,7 +4748,7 @@ int DivEngine::calcBaseFreq(double clock, double divider, int note, bool period)
          base*(divider/clock);
 }
 
-int DivEngine::calcFreq(int base, int pitch, bool period) {
+int DivEngine::calcFreq(int base, int pitch, bool period, int octave) {
   if (song.linearPitch) {
     return period?
             int(base*pow(2,-(double)pitch/(12.0*128.0))/(98.0+globalPitch*6.0)*98.0):
@@ -4756,7 +4756,7 @@ int DivEngine::calcFreq(int base, int pitch, bool period) {
   }
   return period?
            base-pitch:
-           base+pitch;
+           base+((pitch*octave)>>1);
 }
 
 void DivEngine::play() {
diff --git a/src/engine/engine.h b/src/engine/engine.h
index c1421f773..86e708a78 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -266,7 +266,7 @@ class DivEngine {
     int calcBaseFreq(double clock, double divider, int note, bool period);
 
     // calculate frequency/period
-    int calcFreq(int base, int pitch, bool period=false);
+    int calcFreq(int base, int pitch, bool period=false, int octave=0);
 
     // find song loop position
     void walkSong(int& loopOrder, int& loopRow, int& loopEnd);
diff --git a/src/engine/platform/c64.cpp b/src/engine/platform/c64.cpp
index 54259b791..d7f98a2b2 100644
--- a/src/engine/platform/c64.cpp
+++ b/src/engine/platform/c64.cpp
@@ -111,7 +111,7 @@ void DivPlatformC64::tick() {
       rWrite(i*7+4,(isMuted[i]?0:(chan[i].wave<<4))|(chan[i].ring<<2)|(chan[i].sync<<1)|chan[i].active);
     }
     if (chan[i].freqChanged || chan[i].keyOn || chan[i].keyOff) {
-      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch);
+      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,false,8);
       if (chan[i].freq>0xffff) chan[i].freq=0xffff;
       if (chan[i].keyOn) {
         rWrite(i*7+5,(chan[i].attack<<4)|(chan[i].decay));
diff --git a/src/engine/platform/genesis.cpp b/src/engine/platform/genesis.cpp
index f0f54cd1d..9d58e935f 100644
--- a/src/engine/platform/genesis.cpp
+++ b/src/engine/platform/genesis.cpp
@@ -294,7 +294,7 @@ void DivPlatformGenesis::tick() {
   for (int i=0; i<6; i++) {
     if (i==2 && extMode) continue;
     if (chan[i].freqChanged) {
-      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch);
+      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,false,octave(chan[i].baseFreq));
       int freqt=toFreq(chan[i].freq);
       immWrite(chanOffs[i]+ADDR_FREQH,freqt>>8);
       immWrite(chanOffs[i]+ADDR_FREQ,freqt&0xff);
diff --git a/src/engine/platform/ym2610.cpp b/src/engine/platform/ym2610.cpp
index e6018bb0f..4e99b4f01 100644
--- a/src/engine/platform/ym2610.cpp
+++ b/src/engine/platform/ym2610.cpp
@@ -266,7 +266,7 @@ void DivPlatformYM2610::tick() {
   for (int i=0; i<4; i++) {
     if (i==1 && extMode) continue;
     if (chan[i].freqChanged) {
-      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch);
+      chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,false,octave(chan[i].baseFreq));
       int freqt=toFreq(chan[i].freq);
       immWrite(chanOffs[i]+ADDR_FREQH,freqt>>8);
       immWrite(chanOffs[i]+ADDR_FREQ,freqt&0xff);
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index a78077359..134252669 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -537,7 +537,7 @@ void DivEngine::processRow(int i, bool afterDelay) {
           chan[i].portaSpeed=-1;
           chan[i].inPorta=false;
         } else {
-          chan[i].portaNote=0x60;
+          chan[i].portaNote=song.limitSlides?0x60:255;
           chan[i].portaSpeed=effectVal;
           chan[i].portaStop=true;
           chan[i].nowYouCanStop=false;
@@ -552,7 +552,7 @@ void DivEngine::processRow(int i, bool afterDelay) {
           chan[i].portaSpeed=-1;
           chan[i].inPorta=false;
         } else {
-          chan[i].portaNote=disCont[dispatchOfChan[i]].dispatch->getPortaFloor(dispatchChanOfChan[i]);
+          chan[i].portaNote=song.limitSlides?disCont[dispatchOfChan[i]].dispatch->getPortaFloor(dispatchChanOfChan[i]):-255;
           chan[i].portaSpeed=effectVal;
           chan[i].portaStop=true;
           chan[i].nowYouCanStop=false;