In eva(md).ini, this flag, if present, is only set to QUEUE. There are, however, hundreds of sections omitting it, suggesting there's a default value. Whether this is QUEUE or something else is not known.
If this flag is present and set to QUEUE, the voice in it's section will be played after the currently playing voices have finished (the alternative being that it gets ignored).
Note that this questions the use of the alleged QUEUE and QUEUE_INTERRUPT values of Priority. What would you need a priority of QUEUE for, if the type tells the game to queue the sound anyway?
Accepted values
This needs testing
The following section contains information that has not been personally confirmed by the revision's author; readers are encouraged to test it themselves and update the section accordingly.
All of these are case-insensitive. More information is needed to determine their exact effects.