The Scale Step
The scale step is the best known part of Schenker's theory of harmony. His main criticism of roman numeral harmonic analysis is the way that it portrays music as constantly modulating. The crucial difference between Schenker's view and that of Riemann and others is illustrated by their approaches to sonata form.

Where others consider the music to have changed key (into the dominant or relative major), Schenker suggests that all keys other than the tonic are scale steps. He hears them in the same way other analysts might hear a dominant chord - as part of the tonic key. The only difference is that Schenker hears these relationships on a much larger scale.

Schenker, then, understands the tonal system as a balance of opposing forces (the artist and nature) in which every chord and apparent key is in some way part of the tonic. Schenker transforms this from an interesting idea into a coherent theory by understanding music, not as a series of related chords, but as a linear process. In order to do this, Schenker combines his ideas on harmony with a theory of counterpoint.