Adding music is more difficult than I imagined. That is I thought it would be difficult, but it was even more difficult than that. First, it has to be copyright free and second it has to match the mood of the film. Although I found an excellent site offering all sorts of little gems, there was only one that seemed appropriate. Unfortunately it was too short, so I spent hours trying out other music alongside, changing where it started, looping the whole thing so it played twice, looping so just the first section did... In the end I gave up - at least for now. I thought again about what I was trying to achieve and decided I didn't really need music at all. Apart from that one piece which seemed to add to what I was trying to do, the rest seemed like musak and seemed, at least to my ears, to devalue the piece as a whole.
I have decided to look at it again later with a view to doing a standalone piece. I am going to design this to fit the music. Given that I have no sophisticated music software (and no excuse, really, to acquire any) I think this is my best way forward.
However, I have learnt a lot through doing this. I discovered how totally inappropriate some music can be, and was surprised at how it changed how I read my piece. Music manipulates us more than we think, at least more than I thought.