--- gigedit/trunk/src/gigedit/mainwindow.cpp	2021/06/10 12:58:37	3917
+++ gigedit/trunk/src/gigedit/mainwindow.cpp	2021/06/10 13:28:17	3918
@@ -2104,6 +2104,10 @@
 void Loader::thread_function_sub(gig::progress_t& progress)
 {
     RIFF::File* riff = new RIFF::File(filename);
+    // due to the multi-threaded scenario use separate file I/O handles for
+    // each thread to avoid file I/O concurrency issues with .gig file
+    riff->SetIOPerThread(true);
+
     gig = new gig::File(riff);
 
     gig->GetInstrument(0, &progress);
@@ -2217,6 +2221,10 @@
     __clear();
     // create a new .gig file (virtually yet)
     gig::File* pFile = new gig::File;
+    // due to the multi-threaded scenario use separate file I/O handles for
+    // each thread to avoid file I/O concurrency issues with .gig file
+    RIFF::File* pRIFF = pFile->GetRiffFile();
+    pRIFF->SetIOPerThread(true);
     // already add one new instrument by default
     gig::Instrument* pInstrument = pFile->AddInstrument();
     pInstrument->pInfo->Name = gig_from_utf8(_("Unnamed Instrument"));
@@ -3534,6 +3542,21 @@
     file = 0;
     set_file_is_shared(isSharedInstrument);
 
+    // assuming libgig's file-IO-per-thread feature is enabled: by default
+    // the file stream is closed for individual threads (except of the original
+    // thread having opened the gig file), so open the file stream for this
+    // thread for being able to read the .gig file
+    // (see libgig's RIFF::File::SetIOPerThread() for details)
+    ::RIFF::File* riff = gig->GetRiffFile();
+    if (!riff->IsNew() && riff->GetMode() == ::RIFF::stream_mode_closed) {
+        try {
+            riff->SetMode(::RIFF::stream_mode_read);
+        } catch (...) {
+            printf("Failed opening '%s' in read mode\n",
+                   riff->GetFileName().c_str());
+        }
+    }
+
     this->filename =
         (filename && strlen(filename) > 0) ?
             filename : (!gig->GetFileName().empty()) ?