If you're familiar with Stephin Merritt, then you know he's a master songwriter, capable of almost anything. His band The Magnetic Fields is one of many of his creative outputs.
Here's the video of Stephin writing a song in two days in front of the cameras. He wrote it based on a challenge given involving his choosing from six pictures and six words. You have to see the video to see the process. I thought it was interesting, because as I understand it, Stephin is generally a much more planned out songwriter, so this faster style of writing is quite a departure for him, but not a bad one.
