EVENT_OPENMENUSOUND is a Game Event.
Triggered whenever the main menu is opened. RETURN is set to the sound id that is scheduled to play.
Set RETURN to any defined sound number to play that sound when the menu is opened, or set it to -1 to play nothing. This does not affect any other sounds in the menu.
The order of sounds played by the Duke 3D menu when opened is completely deterministic and cycles through the following sequence, starting at index 0.