I haven't heard the piece you're referring to, but i'm guessing the effect is like a tape player coming to a stop. You can simulate this pretty well in Sound Forge with Effects / Pitch / Bend. Trim the end of the file to end at the last part you want to hear, select about a second or so of the end of the file, go to Pitch Bend, set Semitones to 24 (slider all the way to the top), Reset Envelope, then drag the end of the envelope all the way to the bottom. This doesn't quit complete the effect in my opinion as it only slows it down to 1/4 speed. At this point i select about 1/4 second of the end of the file and repeat the bend again. This slows the very end down to 1/16 and finishes it off just about right. You can also fade out the last little bit to cover up the fact that it didn't really stop.

I first tried doing this by selecting about .5 seconds in an attempt to have the entire effect last about 1 second. This seemed too abrupt to me. Having it last twice as long seemed a lot more natural.