Torre Florim has put up an example of on-the-fly songwriting on Ghostnotes:
This was made on a summer night, somewhere in 2010. One of those songs that just ‘happened’.
While I was trying out some new gear in the studio, Jaap, Lea and Jop dropped in. I had a beat, Jaap grabbed the bass, the devil posessed Lea and next thing I know we had a song.
Recorded in our old dusty farm.