uPlayer is called directly through illustrate\dBpoweramp\uPlayer.exe

-zone="device:settings:shownname" if omitted, default is 'waveout:-1:(default)'
-collection="collection_name" if omitted, default is '(global)'
-skipnext skip to next track
-skipprev skip back to begin, or previous track (if < 5 seconds into current)
-pause
-unpause
-stop stops playback (pass zone and collection if not default)
-close close player (zone dependent)
-mute
-unmute
-play="filename" play file
-play (no filename) continue after a stop
-enqueue="filename" queue file  (does not start playing)
-penqueue="filename" priority queue file  (does not start playing)
-volume="x" set volume 1..100
-skippc="x" skip to x %  (0 to 100)

Examples

"c:\program files\illustrate\dbpoweramp\uplayer.exe" // start player
"c:\program files\illustrate\dbpoweramp\uplayer.exe" -enqueue="c:\somefile.mp3" // queue a file (and playback will auto begin)
"c:\program files\illustrate\dbpoweramp\uplayer.exe" -enqueue="c:\anotherfile.mp3" // queue another file

or more advanced:

"c:\program files\illustrate\dbpoweramp\uplayer.exe" -collection="bob" -zone="waveout:1:z1{;}waveout:2:z2" // start player, outputting 'bob' collection to zone 1 & zone 2
"c:\program files\illustrate\dbpoweramp\uplayer.exe" -collection="spoon" -zone="waveout:3:z3" // start player, outputting 'spoon' collection to zone 3
"c:\program files\illustrate\dbpoweramp\uplayer.exe" -collection="bob" -enqueue="c:\somefile.mp3" // queue a file for bob
"c:\program files\illustrate\dbpoweramp\uplayer.exe" -collection="spoon" -enqueue="c:\somefile1.mp3" // queue a file for bob
"c:\program files\illustrate\dbpoweramp\uplayer.exe" -collection="spoon" -pause // pause spoon playback

Noting certain calls to uPlayer.exe will not return if the player is being started, where as others, such as -enqueue return instantly.

uPlayer contains a built in COM object called uPlayer. See examples provided at the end of this section on how to access this object in various languages.
 
Functions:

Set Collection & Zone:  .SetCollectionZone ([in] BSTR Collection, [in] BSTR Zone) 

Collection:    Name of collection, multiple players can be instigated by specifying different collections.
Zone:    Name of the output Zone, output to 2 zones by seperating with {;}, ie. waveout:1:z1{;}waveout:2:z2

If no collection or Zones are specified (ie SetCollectionZone is never called then (global) & waveout:-1:(default) are used for collection and zone. Normally .SetCollection is called once before any of the below functions.