diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index 835636bdd..1f52ad166 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -1223,6 +1223,7 @@ enum DivInsFormats {
   DIV_INSFORMAT_VGI,
   DIV_INSFORMAT_FTI,
   DIV_INSFORMAT_BTI,
+  DIV_INSFORMAT_S3I,
   DIV_INSFORMAT_SBI,
 };
 
@@ -1343,6 +1344,8 @@ bool DivEngine::addInstrumentFromFile(const char* path) {
         format=DIV_INSFORMAT_FTI;
       } else if (extS==String(".bti")) {
         format=DIV_INSFORMAT_BTI;
+      } else if (extS==String(".s3i")) {
+        format = DIV_INSFORMAT_S3I;
       } else if (extS==String(".sbi")) {
         format = DIV_INSFORMAT_SBI;
       }
@@ -1675,6 +1678,85 @@ bool DivEngine::addInstrumentFromFile(const char* path) {
         break;
       case DIV_INSFORMAT_BTI:
         break;
+      case DIV_INSFORMAT_S3I:
+        try {
+          reader.seek(0, SEEK_SET);
+
+          uint8_t s3i_type = reader.readC();
+
+          if (s3i_type >= 2) {
+            ins->type = DIV_INS_OPL;
+            // skip internal filename - we'll use the long name description
+            reader.seek(12, SEEK_CUR);
+
+            // skip reserved bytes
+            reader.seek(3, SEEK_CUR);
+
+            // 12-byte opl value
+            uint8_t s3i_Mcharacteristics = reader.readC();
+            uint8_t s3i_Ccharacteristics = reader.readC();
+            uint8_t s3i_Mscaling_output = reader.readC();
+            uint8_t s3i_Cscaling_output = reader.readC();
+            uint8_t s3i_Meg_AD = reader.readC();
+            uint8_t s3i_Ceg_AD = reader.readC();
+            uint8_t s3i_Meg_SR = reader.readC();
+            uint8_t s3i_Ceg_SR = reader.readC();
+            uint8_t s3i_Mwave = reader.readC();
+            uint8_t s3i_Cwave = reader.readC();
+            uint8_t s3i_FeedConnect = reader.readC();
+            
+            DivInstrumentFM::Operator& opM = ins->fm.op[0];
+            DivInstrumentFM::Operator& opC = ins->fm.op[1];
+            ins->fm.ops = 2;
+            opM.mult = s3i_Mcharacteristics & 0xF;
+            opM.ksr = ((s3i_Mcharacteristics >> 4) & 0x1);
+            opM.sus = ((s3i_Mcharacteristics >> 5) & 0x1);
+            opM.vib = ((s3i_Mcharacteristics >> 6) & 0x1);
+            opM.am = ((s3i_Mcharacteristics >> 7) & 0x1);
+            opM.tl = s3i_Mscaling_output & 0x3F;
+            opM.ksl = ((s3i_Mscaling_output >> 6) & 0x3);
+            opM.ar = ((s3i_Meg_AD >> 4) & 0xF);
+            opM.dr = (s3i_Meg_AD & 0xF);
+            opM.rr = (s3i_Meg_SR & 0xF);
+            opM.sl = ((s3i_Meg_SR >> 4) & 0xF);
+            opM.ws = s3i_Mwave;
+
+            ins->fm.alg = (s3i_FeedConnect & 0x1);
+            ins->fm.fb = ((s3i_FeedConnect >> 1) & 0x7);
+
+            opC.mult = s3i_Ccharacteristics & 0xF;
+            opC.ksr = ((s3i_Ccharacteristics >> 4) & 0x1);
+            opC.sus = ((s3i_Ccharacteristics >> 5) & 0x1);
+            opC.vib = ((s3i_Ccharacteristics >> 6) & 0x1);
+            opC.am = ((s3i_Ccharacteristics >> 7) & 0x1);
+            opC.tl = s3i_Cscaling_output & 0x3F;
+            opC.ksl = ((s3i_Cscaling_output >> 6) & 0x3);
+            opC.ar = ((s3i_Ceg_AD >> 4) & 0xF);
+            opC.dr = (s3i_Ceg_AD & 0xF);
+            opC.rr = (s3i_Ceg_SR & 0xF);
+            opC.sl = ((s3i_Ceg_SR >> 4) & 0xF);
+            opC.ws = s3i_Cwave;
+
+            // Skip more stuff we don't need
+            reader.seek(21, SEEK_CUR);
+          } else {
+            logE("S3I PCM samples currently not supported.");
+          }
+          ins->name = reader.readString(28);
+          int s3i_signature = reader.readI();
+
+          if (s3i_signature != 0x49524353) {
+            logW("S3I signature invalid.");
+          };
+        }
+        catch (EndOfFileException& e) {
+          lastError = "premature end of file";
+          logE("premature end of file!\n");
+          delete ins;
+          delete[] buf;
+          return false;
+        }
+        break;
       case DIV_INSFORMAT_SBI:
         try {
           reader.seek(0, SEEK_SET);
diff --git a/src/engine/safeReader.cpp b/src/engine/safeReader.cpp
index b2b955510..9b096ef79 100644
--- a/src/engine/safeReader.cpp
+++ b/src/engine/safeReader.cpp
@@ -30,14 +30,14 @@ bool SafeReader::seek(ssize_t where, int whence) {
       curSeek=where;
       break;
     case SEEK_CUR: {
-      ssize_t finalSeek=len+where;
+      ssize_t finalSeek=curSeek+where;
       if (finalSeek<0) return false;
       if (finalSeek>(ssize_t)len) return false;
       curSeek=finalSeek;
       break;
     }
     case SEEK_END: {
-      ssize_t finalSeek=len-where;
+      ssize_t finalSeek=curSeek-where;
       if (finalSeek<0) return false;
       if (finalSeek>(ssize_t)len) return false;
       curSeek=finalSeek;
diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index 033ae2f03..ae176447e 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -4658,9 +4658,9 @@ void FurnaceGUI::openFileDialog(FurnaceGUIFileDialogs type) {
       if (!dirExists(workingDirIns)) workingDirIns=getHomeDir();
       hasOpened=fileDialog->openLoad(
         "Load Instrument",
-        {"compatible files", "*.fui *.dmp *.tfi *.vgi, *.sbi",
+        {"compatible files", "*.fui *.dmp *.tfi *.vgi *.s3i *.sbi",
          "all files", ".*"},
-        "compatible files{.fui,.dmp,.tfi,.vgi,.sbi},.*",
+        "compatible files{.fui,.dmp,.tfi,.vgi,.s3i,.sbi},.*",
         workingDirIns,
         dpiScale
       );
@@ -6886,6 +6886,7 @@ bool FurnaceGUI::init() {
 
   ImGuiFileDialog::Instance()->SetFileStyle(IGFD_FileStyleByExtension,".tfi",ImVec4(1.0f,0.5f,0.5f,1.0f),ICON_FA_FILE);
   ImGuiFileDialog::Instance()->SetFileStyle(IGFD_FileStyleByExtension,".vgi",ImVec4(1.0f,0.5f,0.5f,1.0f),ICON_FA_FILE);
+  ImGuiFileDialog::Instance()->SetFileStyle(IGFD_FileStyleByExtension,".s3i",ImVec4(1.0f,0.5f,0.5f,1.0f),ICON_FA_FILE);
   ImGuiFileDialog::Instance()->SetFileStyle(IGFD_FileStyleByExtension,".sbi",ImVec4(1.0f,0.5f,0.5f,1.0f),ICON_FA_FILE);
   ImGuiFileDialog::Instance()->SetFileStyle(IGFD_FileStyleByExtension,".fti",ImVec4(1.0f,0.5f,0.5f,1.0f),ICON_FA_FILE);
   ImGuiFileDialog::Instance()->SetFileStyle(IGFD_FileStyleByExtension,".bti",ImVec4(1.0f,0.5f,0.5f,1.0f),ICON_FA_FILE);