Here's an example of "found" music.
This is something I often do for amusement- come across something and try to find a way to turn it into a musical score.
In this instance, I traced a picture of Vancouver, British Columbia, Canada's Lions Gate Bridge onto manuscript paper and literally turned the shape of the bridge into music.
You'll see this if you look at the opening of the score.
The rest of the piece is made up of elements based on this basic shape.
This is just one example of "found" music.