The Roman number system for describing changes used in this project is based on that used by Mehegan, in that it uses letters M, x, m, Ø and o to indicate chord quality, but it also uses upper/lower case numbering to distinguish major from minor or diminished chords. This means there is redundancy, since the Mehegan system already defines a chord as major, minor, half diminished or diminished, but the case system is retained to make it more quickly comprehensible to those who are unused to the Mehegan system.

Like Mehegan's system, the chord quality defaults to the quality of the chord that is diatonic to the key. Thus chord I has type M, chord ii has type m, chord vii type o, etc. unless otherwise specified.

All chords are considered to be 6ths/7ths. There is no way to specify a triad, as it is believed a triad will have an implied quality defined by the 7th that could be added to it. There is no way of specifying extensions, since these don't add anything to the fundamental character of the chord. There is no distinction between different chords within these categories. There is some argument for providing more categories - e.g. to distinguish minor 6th from minor 7th, or to distinguish sus or 11th chords from other dominant chords.

In text, rather than the charts, further detail may be added. For example alterations may be expressed by adding the alteration directly to the basic chord description, e.g. VIx#9.

Key changes may occur during a piece, if that makes the chart easier to analyse. This would be indicated by e.g. "Key: bVI (+4b)" or "Original Key:"