--- linuxsampler/trunk/src/engines/common/InstrumentScriptVM.cpp	2021/06/24 11:49:31	3970
+++ linuxsampler/trunk/src/engines/common/InstrumentScriptVM.cpp	2021/06/25 09:26:00	3971
@@ -106,9 +106,37 @@
         AbstractInstrumentManager* pManager =
             dynamic_cast<AbstractInstrumentManager*>(pEngineChannel->pEngine->GetInstrumentManager());
 
-        // get new script reference
-        parserContext = pManager->scripts.Borrow(
-            { .code = text, .patchVars = patchVars }, pEngineChannel
+        /*
+           Get new script reference.
+
+           Note: every engine channel now has its own compiled script object
+           (a.k.a. VMParserContext). Originally a compiled script was shared by
+           multiple engine channels. This was wrong: we cannot share compiled
+           script instances among multiple engine channels (parts), for two
+           reasons:
+
+           1. VMParserContext not only encompasses the compiled tree
+              presentation of the requested script, but also global variables
+              and we don't want those global variables to be modified by
+              different sampler parts, as this would not be expected behaviour
+              by instrument script authors.
+
+           2. If there is more than one sampler engine instance (e.g. if there
+              are multiple audio output device instances) this would even crash,
+              because each sampler engine instance has its own ScriptVM
+              instance, and a (VM)ParserContext is always tied to exactly one
+              ScriptVM instance.
+
+           We would not be buying much by sharing compiled scripts anyway, as a
+           script usually compiles in couple microseconds and RAM usage is also
+           neglectable.
+        */
+        parserContext = pManager->scripts.Borrow({
+                .code = text,
+                .patchVars = patchVars,
+                .engineChannel = pEngineChannel /* unique owner of script */
+            },
+            pEngineChannel /* who is asking to borrow */
         );
         if (!parserContext->errors().empty()) {
             std::vector<ParserIssue> errors = parserContext->errors();