ported #6891: Improves recognition of instrument when loading a pre-3…

….6 score.

src/libmscore/instrument.cpp

@@ -1720,14 +1720,44 @@ void Instrument::updateInstrumentId()
         return;
     }
 
+    // When reading a score create with pre-3.6, instruments doesn't
+    // have an id define in the instrument. So try to find the instrumentId
+    // based on MusicXMLid.
+    // This requires a hack for instruments using MusicXMLid "strings.group"
+    // because there are multiple instrument using this same id.
+    // For these instruments, use the value of controller 32 of the "arco"
+    // channel to find the correct instrument.
+    const QString arco = QString("arco");
+    const bool groupHack = instrumentId() == QString("strings.group");
+    const int idxref = channelIdx(arco);
+    const int val32ref = (idxref < 0) ? -1 : channel(idxref)->bank();
+    QString fallback;
+
     for (InstrumentGroup* g : qAsConst(instrumentGroups)) {
         for (InstrumentTemplate* it : qAsConst(g->instrumentTemplates)) {
             if (it->musicXMLid == instrumentId()) {
-                _id = it->id;
-                return;
+                if (groupHack) {
+                    if (fallback.isEmpty()) {
+                        // Instrument "Strings" doesn't have bank defined so
+                        // if no "strings.group" instrument with requested bank
+                        // is found, assume "Strings".
+                        fallback = it->id;
+                    }
+                    for (const Channel& chan : it->channel) {
+                        if ((chan.name() == arco) && (chan.bank() == val32ref)) {
+                            _id = it->id;
+                            return;
+                        }
+                    }
+                } else {
+                    _id = it->id;
+                    return;
+                }
             }
         }
     }
+
+    _id = fallback.isEmpty() ? QString("piano") : fallback;
 }
 
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