The seven white notes on the piano - each section of the piece (there are 12 sections) is five of those seven white notes. If you calculate it, there are 21 groups of five notes in any group of seven notes. And although there are 12 sections, this piece actually uses nine of those groups because some of the sections repeat earlier ones. So that's the formula. It's very simple as a way of generating something. It's my inner minimalist.