- consider the volume control of all Windows MIDI mapper devices broken, because it may be the GS synth, which is not detectable.

src/sound/mididevices/music_win_mididevice.cpp

@@ -659,17 +659,29 @@ void CALLBACK WinMIDIDevice::CallbackFunc(HMIDIOUT hOut, UINT uMsg, DWORD_PTR dw
 
 static bool IgnoreMIDIVolume(UINT id)
 {
-#ifndef __GNUC__
 	MIDIOUTCAPS caps;
+	bool mustcheck = false;
 
 	if (MMSYSERR_NOERROR == midiOutGetDevCaps(id, &caps, sizeof(caps)))
 	{
+		if (caps.wTechnology == MIDIDEV_MAPPER)
+		{
+			// We cannot determine what this is so we have to assume the worst, as the default
+			// devive's volume control is irreparably broken.
+			mustcheck = true;
+		}
 		// The Microsoft GS Wavetable Synth advertises itself as MIDIDEV_SWSYNTH with a VOLUME control.
 		// If the one we're using doesn't match that, we don't need to bother checking the name.
 		if (caps.wTechnology == MIDIDEV_SWSYNTH && (caps.dwSupport & MIDICAPS_VOLUME))
 		{
 			if (strncmp(caps.szPname, "Microsoft GS", 12) == 0)
 			{
+				mustcheck = true;
+			}
+		}
+		if (mustcheck)
+		{
+#ifndef __GNUC__
 			IMMDeviceEnumerator *enumerator;
 
 			// Now try to create an IMMDeviceEnumerator interface. If it succeeds,
@@ -682,10 +694,12 @@ static bool IgnoreMIDIVolume(UINT id)
 				enumerator->Release();
 				return true;
 			}
-			}
-		}
-	}
+#else
+			// assume the worst and consider volume control broken.
+			return true;
 #endif
+		}
+	}
 	return false;
 }