diff --git a/src/gui/gui.h b/src/gui/gui.h
index 1abe9d9e3..b3393a5a9 100644
--- a/src/gui/gui.h
+++ b/src/gui/gui.h
@@ -1086,6 +1086,7 @@ class FurnaceGUI {
     int doubleClickColumn;
     int blankIns;
     int dragMovesSelection;
+    int unsignedDetune;
     unsigned int maxUndoSteps;
     String mainFontPath;
     String patFontPath;
@@ -1187,6 +1188,7 @@ class FurnaceGUI {
       doubleClickColumn(1),
       blankIns(0),
       dragMovesSelection(1),
+      unsignedDetune(0),
       maxUndoSteps(100),
       mainFontPath(""),
       patFontPath(""),
diff --git a/src/gui/insEdit.cpp b/src/gui/insEdit.cpp
index 646be8b50..45f7c6757 100644
--- a/src/gui/insEdit.cpp
+++ b/src/gui/insEdit.cpp
@@ -1894,11 +1894,11 @@ void FurnaceGUI::drawInsEdit() {
                     }
 
                     if (ins->type==DIV_INS_FM || ins->type==DIV_INS_OPZ) {
-                      int detune=(op.dt&7)-3;
+                      int detune=(op.dt&7)-(settings.unsignedDetune?0:3);
                       ImGui::TableNextColumn();
                       CENTER_VSLIDER;
                       if (CWVSliderInt("##DT",ImVec2(20.0f*dpiScale,sliderHeight),&detune,-3,4)) { PARAMETER
-                        op.dt=detune+3;
+                        op.dt=detune+(settings.unsignedDetune?0:3);
                       }
 
                       ImGui::TableNextColumn();
@@ -2224,11 +2224,11 @@ void FurnaceGUI::drawInsEdit() {
                           snprintf(tempID,1024,"%s: %%d",FM_NAME(FM_MULT));
                           P(CWSliderScalar("##MULT",ImGuiDataType_U8,&op.mult,&_ZERO,&_FIFTEEN,tempID)); rightClickable
 
-                          int detune=(op.dt&7)-3;
+                          int detune=(op.dt&7)-(settings.unsignedDetune?0:3);
                           ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x);
                           snprintf(tempID,1024,"%s: %%d",FM_NAME(FM_DT));
                           if (CWSliderInt("##DT",&detune,-3,4,tempID)) { PARAMETER
-                            op.dt=detune+3;
+                            op.dt=detune+(settings.unsignedDetune?0:3);
                           } rightClickable
 
                           ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x);
@@ -2369,11 +2369,11 @@ void FurnaceGUI::drawInsEdit() {
                             snprintf(tempID,1024,"%s: %%d",FM_NAME(FM_MULT));
                             P(CWSliderScalar("##MULT",ImGuiDataType_U8,&op.mult,&_ZERO,&_FIFTEEN,tempID)); rightClickable
 
-                            int detune=(op.dt&7)-3;
+                            int detune=(op.dt&7)-(settings.unsignedDetune?0:3);
                             ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x);
                             snprintf(tempID,1024,"%s: %%d",FM_NAME(FM_DT));
                             if (CWSliderInt("##DT",&detune,-3,4,tempID)) { PARAMETER
-                              op.dt=detune+3;
+                              op.dt=detune+(settings.unsignedDetune?0:3);
                             } rightClickable
                           }
 
@@ -2666,12 +2666,12 @@ void FurnaceGUI::drawInsEdit() {
                       ImGui::Text("%s",FM_NAME(FM_MULT));
                       
                       if (ins->type==DIV_INS_FM || ins->type==DIV_INS_OPZ) {
-                        int detune=(op.dt&7)-3;
+                        int detune=(op.dt&7)-(settings.unsignedDetune?0:3);
                         ImGui::TableNextRow();
                         ImGui::TableNextColumn();
                         ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x);
                         if (CWSliderInt("##DT",&detune,-3,4)) { PARAMETER
-                          op.dt=detune+3;
+                          op.dt=detune+(settings.unsignedDetune?0:3);
                         } rightClickable
                         ImGui::TableNextColumn();
                         ImGui::Text("%s",FM_NAME(FM_DT));
diff --git a/src/gui/settings.cpp b/src/gui/settings.cpp
index bdcc2de80..cb2064e62 100644
--- a/src/gui/settings.cpp
+++ b/src/gui/settings.cpp
@@ -1197,6 +1197,11 @@ void FurnaceGUI::drawSettings() {
           if (ImGui::Checkbox("Use German notation",&germanNotationB)) {
             settings.germanNotation=germanNotationB;
           }
+
+          bool unsignedDetuneB=settings.unsignedDetune;
+          if (ImGui::Checkbox("Unsigned FM detune values",&unsignedDetuneB)) {
+            settings.unsignedDetune=unsignedDetuneB;
+          }
           
           // sorry. temporarily disabled until ImGui has a way to add separators in tables arbitrarily.
           /*bool sysSeparatorsB=settings.sysSeparators;
@@ -2049,6 +2054,7 @@ void FurnaceGUI::syncSettings() {
   settings.doubleClickColumn=e->getConfInt("doubleClickColumn",1);
   settings.blankIns=e->getConfInt("blankIns",0);
   settings.dragMovesSelection=e->getConfInt("dragMovesSelection",2);
+  settings.unsignedDetune=e->getConfInt("unsignedDetune",0);
 
   clampSetting(settings.mainFontSize,2,96);
   clampSetting(settings.patFontSize,2,96);
@@ -2134,6 +2140,7 @@ void FurnaceGUI::syncSettings() {
   clampSetting(settings.doubleClickColumn,0,1);
   clampSetting(settings.blankIns,0,1);
   clampSetting(settings.dragMovesSelection,0,2);
+  clampSetting(settings.unsignedDetune,0,1);
 
   settings.initialSys=e->decodeSysDesc(e->getConfString("initialSys",""));
   if (settings.initialSys.size()<4) {
@@ -2268,6 +2275,7 @@ void FurnaceGUI::commitSettings() {
   e->setConf("doubleClickColumn",settings.doubleClickColumn);
   e->setConf("blankIns",settings.blankIns);
   e->setConf("dragMovesSelection",settings.dragMovesSelection);
+  e->setConf("unsignedDetune",settings.unsignedDetune);
 
   // colors
   for (int i=0; i<GUI_COLOR_MAX; i++) {