Well... they way I do it is whenever I want to find the name of an effect (music or voice called using a trigger), I place one in mission with that effect selected and save the mission.
Then using a text editor (wordpad or notepad), I open up the mission.sqm file and find the entry for the trigger.
Down the bottom there will be an 'effects' section. The name of your music (or voice file) should be listed in there