I made this altered soundscape, which I call "Closing" (you can see why in the middle of the piece), as part of
this challenge, which asks that you add an imperceptible sound to a field recording, then make it become more obvious.
I found the imperceptible part really hard because I know where the added sound came from, and therefore can always perceive it. I did run it by Katt, and it didn't jump out at her, so I counted it as good enough since I didn't have time to survey a whole bunch of people.
I don't know if I'll think of this as "successful" in a month, but it was indeed a good exercise.