The primary focus of the work is upon a chord named by the author, the diminished-major, symbolized as oM, which has current history in modern and mainstream jazz practice, as well as in classical music theory, but which has not up to now been so uniquely identified.  The chord and its symbol are based solidly upon accepted music theory - diminished scaletone notes set to chords in a form suitable for the work of both the improvisator as well as the notational composer. 

Besides being an aid for musicians to develop along fresh lines from within the mainstream idiom, Concept also shows that it is possible to approach even that which is called atonal, or out, improvised playing in a studious and regulated manner.

By way of its diminished-major chords, a Quarto-Mode can be a self-contained organized relationship of tones - an enclosed micro-system.  The chord with its symbol is a tool inside a concept called a Quarto-Mode with which to shape new music.