You may have a shot at getting something to work, but only on Windows, then you may have to use MDI, or whatever windows calls it's standard. On linux, it would be impossible because all the apps are so different.

My first try would be to make everything the "child" of a Tk app, and have a little Tk window open for dropping DnD objects into. You can use DND between Tk apps, so make a Tk wrapper around SoundForge and/or PrtTools, which starts up, and runs them thru IPC::Run, and creates a little 1 inch square canvas to drop onto. When the drop-recepticle gets an object dropped on it, it passes it on to the other apps thru IPC.

All in all it sounds like it would get complicated and very "troubleprone" to deal with. Unless you are a "software pioneer", it would be best to think of other ways....like making a temp file and passing data that way.