It seems to play from MIDs replayed in Cubase with PTQ4 as VST, and changes to a fresh 'scene' in order to accommodate change of Pianoteq preset between one scene' and the next. In a later vid, Rhody etc get their turn, but this is straight D4. At one point, a live demo involving exploration/tinkering with various recording possibilities turns up, with flickbacks to start-of-MID used, showing just how conveniently this can be done in Cubase. As for where the MIDs derive from who knows, Notion, anywhere...

As I've linked it, the Electric Pianos demo seems to be one button in the matrix resulting from end-of-play, and is also in the list of 'suggestions' at right.