sointuoppi

Sointuoppi, or harmony theory, is a branch of music theory that studies chords, their construction and their functional role within a tonal system. It explains how different chords relate to each other through key centers and how chord progressions create a sense of movement and resolution in a piece of music.

Core topics include diatonic triads in major and minor keys, and the qualities of these triads (major, minor, diminished), as well as seventh chords such as major seventh, dominant seventh, minor seventh, and half-diminished. The concept of functional harmony organizes chords into roles—tonic, subdominant, and dominant—and describes common progressions, cadences, and voice-leading rules. An advanced focus is modulation and key changes, which use pivot chords, common tones, and chromatic voice-leading. Borrowed chords and modal mixture provide color outside strict diatonic harmony. Analysts typically use Roman numerals and chord symbols to describe harmonic structure.

In Finland, sointuoppi is taught as part of school and university music theory, and it underpins both classical analysis and the study of pop, rock, and other Western tonal music. While rooted in traditional harmony, the subject also informs contemporary composition and arrangement, where rules may be expanded or adapted.

The term is closely connected to broader concepts in Western music theory, including tonality, voice leading, and form, and it serves as a foundation for analyzing a wide range of repertoires from classical to contemporary popular music.