EVENT PLAYLEVELMUSICSLOT
EVENT_PLAYLEVELMUSICSLOT is a Misc Event.
Called when a music track will be started from the beginning (excluding loops), regardless of whether the music is on or off.
The slot of the requested track is passed into EVENT_PLAYLEVELMUSICSLOT via the userdef struct members m_volume_number and m_level_number.
Set RETURN to -1 in order to disable the music for the map.