Lanux128, try AHK_xmplay_input_to_playlist_DDEML   v080821

;-----------------------------------
; autohotkey script for silently adding to Xmplay playlist through DDE
;  takes file(s)/folder(s)/playlist(s) as input parameter
; - drop input on AHK_xmplay_input_to_playlist_DDEML.exe or
; - pass input as quote enclosed, space separated command line parameters
;  (use no end slash for folders!)
;   example: C:\AHK_xmplay_input_to_playlist_DDEML.exe "C:\musicfolder" "C:\music2\song.mp3"
;
; made by nod5 , version 080821
; using DDEML by sean, http://www.autohotkey.com/forum/topic19169.html
;-----------------------------------

The attached zip includes:
68b207b3d1dca7511752b8fd8a2d3cac *AHK_xmplay_input_to_playlist_DDEML.ahk
390dc531993efe6af2ac7d271f2d8712 *AHK_xmplay_input_to_playlist_DDEML.exe

note: to add all input files one by one to Xmplay playlist through DDE took noticeably long time. To speed things up I let the script first make a temporary .pls playlist file containing all input files, then add the .pls to Xmplay though DDE, then delete the .pls. Xmplay automatically adds all files from the .pls.

note2: there might be some upper limit to the number of files or total length of the command line string that can be passed to the script, though I haven't looked into that (it is not built in by me but might be due to some limit in autohotkey or windows)

As far as I know you can only use command line to open files (which clears any previous track from the playlist).
http://support.xmplay.com/article.php?id=35

Opening Files
This is done by giving the full path name to XMPlay. For example:
"c:\XMPlay.exe" "c:\Music\Garbage - Supervixen.ogg"
And multiple songs:
"c:\XMPlay.exe" "c:\Music\Garbage - Supervixen.ogg" "c:\Music\Creed - One.ogg"
Opening Folders
This is done by giving the full path of the directory to XMPlay. For example:
"c:\XMPlay.exe" "c:\Music\Ogg\"
And multiple directories:
"c:\XMPlay.exe" "c:\Music\Ogg\" c:\Music\Mp3\"

Adding files can be done through DDE via autohotkey. See the ahk source for my small scripts above for details and http://support.xmplay.com/article.php?id=17 . I also want to be able to add files to the xmplay playlist (specifically from the FARR plugin albumdisplayer that I've been working on) so I'll sooner or later try to make a small AHK script that just takes one or more file paths as input and then silently adds them to the xmplay playlist. If you don't make it first that is  ;D

AlbumDisplayer v080813 v080814
-- link removed, use newer version below -- (md5 ebb905356dd7aa7e3a27ece19302de1e)
changelog:
v080814
- folders with ' in path now works
v080813
- now trims all % in input to avoid FARR crash (example: "alb abc%" previously caused crash)
- special search phrase "alb *" displays all albums (first 100 then 50 more at each scroll to page bottom)
- ctrl+click album to open its folder

Let me hear your impressions on "alb *" - does it freeze FARR too long/too often?