diff --git a/src/sound/fmodsound.cpp b/src/sound/fmodsound.cpp
index 21ba53b5b..b01754324 100644
--- a/src/sound/fmodsound.cpp
+++ b/src/sound/fmodsound.cpp
@@ -1598,6 +1598,7 @@ SoundStream *FMODSoundRenderer::OpenStream(const char *filename_or_data, int fla
 	FMOD::Sound *stream;
 	FMOD_RESULT result;
 	bool url;
+	FString patches;
 
 	InitCreateSoundExInfo(&exinfo);
 	mode = FMOD_SOFTWARE | FMOD_2D | FMOD_CREATESTREAM;
@@ -1614,7 +1615,20 @@ SoundStream *FMODSoundRenderer::OpenStream(const char *filename_or_data, int fla
 	exinfo.fileoffset = offset;
 	if ((*snd_midipatchset)[0] != '\0')
 	{
-		exinfo.dlsname = snd_midipatchset;
+#ifdef _WIN32
+		// If the path does not contain any path separators, automatically
+		// prepend $PROGDIR to the path.
+		if (strcspn(snd_midipatchset, ":/\\") == strlen(snd_midipatchset))
+		{
+			patches << "$PROGDIR/" << snd_midipatchset;
+			patches = NicePath(patches);
+		}
+		else
+#endif
+		{
+			patches = NicePath(snd_midipatchset);
+		}
+		exinfo.dlsname = patches;
 	}
 
 	url = (offset == 0 && length == 0 && strstr(filename_or_data, "://") > filename_or_data);
diff --git a/src/sound/music_fluidsynth_mididevice.cpp b/src/sound/music_fluidsynth_mididevice.cpp
index d50e236b7..7914aa256 100644
--- a/src/sound/music_fluidsynth_mididevice.cpp
+++ b/src/sound/music_fluidsynth_mididevice.cpp
@@ -42,6 +42,7 @@
 #include "m_swap.h"
 #include "w_wad.h"
 #include "v_text.h"
+#include "cmdlib.h"
 
 // MACROS ------------------------------------------------------------------
 
@@ -471,7 +472,21 @@ int FluidSynthMIDIDevice::LoadPatchSets(const char *patches)
 	count = 0;
 	while (tok != NULL)
 	{
-		if (FLUID_FAILED != fluid_synth_sfload(FluidSynth, tok, count == 0))
+		FString path;
+#ifdef _WIN32
+		// If the path does not contain any path separators, automatically
+		// prepend $PROGDIR to the path.
+		if (strcspn(tok, ":/\\") == strlen(tok))
+		{
+			path << "$PROGDIR/" << tok;
+			path = NicePath(path);
+		}
+		else
+#endif
+		{
+			path = NicePath(tok);
+		}
+		if (FLUID_FAILED != fluid_synth_sfload(FluidSynth, path, count == 0))
 		{
 			DPrintf("Loaded patch set %s.\n", tok);
 			count++;