in the my music tab, Unk5 appears to be the amount of time a song waits before it begins playing. two songs that do this are on XStadium: H01_PM_MainTheme, and H06_RS_ChampionRoad. songs that start playing exactly on GO!, like A09_LM_Theme and A60_GLX2_ThemeofSMG2, have their Unk5 set to 4294967295.