https://github.com/sirjuddington/SLADE/issues/1147

diff -Naur a/src/Audio/MIDIPlayer.cpp b/src/Audio/MIDIPlayer.cpp
--- a/src/Audio/MIDIPlayer.cpp	2020-05-28 00:08:34.000000000 +0100
+++ b/src/Audio/MIDIPlayer.cpp	2020-05-31 21:40:03.480211253 +0100
@@ -74,8 +74,6 @@
 #ifndef NO_FLUIDSYNTH
 	// Set fluidsynth driver to alsa in linux (no idea why it defaults to jack)
 #if !defined __WXMSW__ && !defined __WXOSX__
-	if (fs_driver == "")
-		fs_driver = "alsa";
 #endif // !defined __WXMSW__ && !defined __WXOSX__
 
 	// Init soundfont path