It's surprising that the music ever played, now that I checked the files. There is no new descr_sounds_accents file that allocates sound to the faction. Do you get any sound on the strat map?
If so then some default mechanism takes care of that (need to check after installing the sub mod again). In the meantime go to the mods\SS6.3\data\world\maps\base directory and open the descr_sounds_music_types file with Notepad and add sweden to the first 'factions' line:
Code:
factions sweden denmark scotland france hre england teutonic_order norway jerusalem
Open the descr_sounds_accents file (not supplied by the sub mod) in the data folder, check if sweden exists and if not add sweden to the East European accent
Code:
accent East_European
factions sweden kievan_rus, russia, poland, hungary, denmark, norway, lithuania
Now delete the events.idx and dat files in the data\sounds folder and start the mod.
I'll have a deeper look into it and will make sure to correct that issue with an updated fix.