Chord (music)

Lore & Background

Between the 16th and 18th centuries, chords developed into primary musical elements distinct from their polyphonic origins. In early church polyphony known as organum, a plainsong was paired with another melody, and chords were incidental results of the melodic lines. During the Renaissance, polyphony became more complex, and seventh chords started to appear in the 16th century. In the Baroque era, seventh chords began to function in specific ways that enabled smooth voice leading and complex cadences, with the dominant seventh chord becoming a fixture of classical music during the common practice period. The era also saw the rise of figured bass notation, where numbers indicate the harmony above each bass note.

Reader's Guide

Chords are identified by their intervals, with the four basic triad qualities being major, minor, diminished, and augmented. The major chord occurs in harmonics 4, 5, and 6 of the harmonic series. Theorists began analyzing chord structure in the 16th century, and Jean-Philippe Rameau developed the nomenclature for chord inversion still in use today. Root position places the root as the lowest note; first inversion puts the third in the bass; second inversion puts the fifth in the bass. Hugo Riemann built on Rameau's work to develop functional harmony, where every chord is analyzed by its relationship to the tonic or dominant. In the 20th century, composers expanded tonality, structuring chords in fourths and fifths, and using tone clusters made of small intervals. Jazz has a particularly eclectic chord vocabulary, and extended chords are one of its central characteristics.

Did You Know?

• The term 'chord' derives from 'accord', which became 'cord' in Middle English, and the spelling was changed to 'chord' in the 17th century to prevent confusion with 'cord'.
• An arpeggio is a chord where notes are sounded separately.
• The dominant seventh chord became a fixture of classical music during the common practice period.
• The Nashville Number System is a 20th-century shorthand for labeling chords.

From Polyphony to Chord: A Historical Arc

The word "chord" traces back to the Latin "accord," meaning agreement or harmonious sound, which entered Middle English as "cord" before being respelled in the 17th century to avoid confusion with "cord." Until the Middle Ages, harmony simply meant any pairing of two notes. It was not until the Renaissance that the simultaneous sounding of three notes became the working definition of harmony. In early church organum, a plainchant was doubled at a perfect interval—fourth, fifth, or octave—and any chords that emerged were incidental byproducts of the melodic lines. By the 16th century, seventh chords appeared, and in the Baroque era they took on specific functional roles that enabled smooth voice leading and complex cadences. The dominant seventh chord became a cornerstone of classical music during the common practice period. As tonality expanded, composers incorporated chromatic structures like Neapolitan and augmented sixth chords, eventually stripping functional purpose from these sonorities and valuing them purely for their sonic color. The 20th century pushed chord vocabulary even further, embracing dissonance, tone clusters, and microtonal intervals.

Anatomy of a Chord: Structure and Qualities

A triad, the most fundamental chord, consists of three notes: a root, a third, and a fifth, all identified by their intervallic distance from the root. The major triad appears naturally within the harmonic series, specifically in harmonics 4, 5, and 6. Stacking additional thirds above the basic triad produces seventh, ninth, eleventh, and thirteenth chords before cycling back to the root. Sonorities larger than a tetrad are sometimes called polychords, as they can be interpreted as two distinct chords layered together. Four basic triad qualities exist: major and minor, which differ in the quality of their third, and diminished and augmented, which differ in the quality of their fifth. Jean-Philippe Rameau, working from the 16th century onward, established the nomenclature for chord inversion still in use today. In root position, the root is the lowest pitch. First inversion places the third in the bass, while second inversion puts the fifth at the bottom, a position long regarded as dissonant even as composers adopted it into regular practice. Extended chords, built from stacked thirds beyond the seventh, became a defining feature of jazz harmony.

Functional Harmony: How Chords Relate and Resolve

The theoretical framework for understanding chord relationships was shaped by two key figures. Jean-Philippe Rameau developed the system of chord inversion nomenclature, and Hugo Riemann later built upon that foundation to articulate functional harmony, in which every chord is analyzed by its relationship to either the tonic or the dominant. Chords inherited their behavioral patterns from the part-writing traditions of polyphonic music. The inner voices of a chord mirror the same intervallic relationships as their melodic ancestors. A classic example is the dominant seventh chord: its inherent tritone dissonance resolves stepwise in traditional voice leading, with the seventh descending to the third and the leading tone ascending to the tonic. A simple progression moving from tonic to dominant and back served as the structural template for countless short compositions. As music grew more chromatic, composers borrowed chords from other keys without formally modulating, and altered chords obscured root relationships to the point where tonality could be asserted merely through a composer's emphasis rather than through strict functional logic.

Notation, Progression, and the Living Vocabulary of Chords

Chords can be notated in several systems, including figured or thorough bass, Roman numerals, the Nashville Number System, and alphabetical chord notation. Figured bass, which emerged during the Baroque era, pairs a bass melody with numbers indicating the harmony to be played above each note, a practical shorthand when counterpoint was no longer the imperative. A chord progression is a sequence of harmonies directed toward a specific musical purpose, such as reinforcing the tonic or modulating to a new pitch center. These progressions are a hallmark of Western music, and homophonic textures where melody and harmony move in unison remain central to classical music instruction. An arpeggio, in which chord notes are sounded successively rather than simultaneously, represents a broken-chord variant. Chords can also be implied within a melody without being explicitly sounded. In contemporary practice, jazz has developed a particularly eclectic chord vocabulary, while 20th-century composers expanded tonality by structuring chords in fourths and fifths for greater ambiguity, or compressing them into tone clusters of small intervals like seconds, creating dense sound masses that became a signature of modern composition.

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