The transition from chord types, which refers to the traditional, tertian sounds, to formations, meaning the interval structures of the 20th century, is still considered one of the most significant upheavals in recent music history. This book aims to illustrate this evolution. Beginning with the phenomena present in the late Baroque, such as sequences and transpositions, and various four-note chords like the Dv and function-specific four-note chords, it then moves on to chord extensions of the Romantic era, as seen in the works of Chopin and Schumann, as well as alterations and dissonances. Scales, modes, and tonality further enrich the spectrum. The increasing dissolution of chord consistency in the late Romantic period leads to interval-oriented structures in 20th-century music, which are demonstrated through examples of sacred works and variations, alongside individual aspects such as augmented triads and quartal harmony.