On many Linux environments, you can add custom entries to its launcher
  by modifying the .desktop file. For Canonical's Unity documentation,
  see Adding Shortcuts to a Launcher. For details on a
  more generic implementation, see the freedesktop.org Specification.
Launcher shortcuts of Audacious:

Generally speaking, shortcuts are added by providing a Name and Exec
  property for each entry in the shortcuts menu. Unity will execute the
  Exec field once clicked by the user. The format is as follows:
Actions=PlayPause;Next;Previous
  
  [Desktop Action PlayPause]
  Name=Play-Pause
  Exec=audacious -t
  OnlyShowIn=Unity;
  
  [Desktop Action Next]
  Name=Next
  Exec=audacious -f
  OnlyShowIn=Unity;
  
  [Desktop Action Previous]
  Name=Previous
  Exec=audacious -r
  OnlyShowIn=Unity;Unity's preferred way of telling your application what to do is to use
  parameters. You can find these in your app in the global variable
  process.argv.