Root (chord) - Root Progressions in Music

Root Progressions in Music

Jean-Philippe Rameau introduced the theory of chord roots in his Traité de l'harmonie (1722). Subsequently, the analysis and theory of tonal music has typically treated chordal roots as the defining feature of harmony. Because inverting a chord simply reshuffles the same pitch material, chords of the same root sound and function similarly. Rameau's insight led him to describe chord-to-chord movements in terms of the interval between the chordal roots, instead of their bass notes. Allowing for octave equivalence, root progressions of a second, third, or fourth are possible in a diatonic context.

By using Roman numeral analysis, musicians describe harmonic progressions in reference to a given key's tonic pitch. "Individual chord progressions can be analyzed in terms of the interval formed between their roots." Such analyses reveal similarities between music which might be in different keys or employ different chordal inversions.

Why is it so important to know the root of the chord? Because the roots of the chords will sound whether we want them to or not, whether or not the alphabetical symbol is correct. The root progression which emerges may not coincide with what we think we have written; it may be better or it may be worse; but art does not permit chance. The root progression supports the work. The total root progression is heard as a substantive element, almost like another melody, and it determines the tonal basis of the music. And the tonal basis of a piece is very important to the construction of themes and to the orchestration. —Russo (1975).