Computational Creativity and Music - Computational Creativity Research: Towards Creative Machines - page 310

Fig. 15.5 Eight completions of the same four note beginning, four by human composers (not the
author) and four by the simple computer program described in the text
15.3.2 Harmony
Harmony in Classical-style music follows very defined vertical and horizontal rules.
In brief, these rules consist of triads and stepwise motion of horizontal lines. There
are, of course, exceptions to these rules such as certain seventh chords as harmonies