Chord (music) - Definition and History

Definition and History

The English word "chord" derives from Middle English "cord", a shortening of "accord" in the original sense of "agreement" and later "harmonious sound". A sequence of chords is known as a chord progression or harmonic progression. These are frequently used in Western music. A chord progression "aims for a definite goal" of establishing (or contradicting) a tonality founded on a key, root or tonic chord. The study of harmony involves chords and chord progressions, and the principles of connection that govern them.

Otto Karolyi writes that "two or more notes sounded simultaneously are known as a chord" though, since instances of any given note in different octaves may be taken as the same note, it is more precise for the purposes of analysis to speak of distinct "pitch classes". Furthermore, as three notes are needed to define any common chord, three is often taken as the minimum number of notes that form a definite chord. Hence Andrew Surmani, for example, (2004, p. 72) states; "when three or more notes are sounded together, the combination is called a chord" and George T. Jones (1994, p. 43) agrees; "two tones sounding together are usually termed an interval, while three or mores tones are called a chord". According to Monath (1984, p. 37); "A chord is a combination of three or more tones sounded simultaneously" and the distances between the tones are called intervals. However sonorities of two pitches, or even single-note melodies, are commonly heard as "implying" chords.

For a sound configuration to be recognized as a chord it must have a certain duration. But, since a chord may be understood as such even when all its notes are not simultaneously audible, there has been some academic discussion regarding the point at which a group of notes may be called a chord. Jean-Jacques Nattiez (1990, p. 218) explains that "we can encounter 'pure chords' in a musical work," such as in the "Promenade" of Modest Mussorgsky's Pictures at an Exhibition but "often, we must go from a textual given to a more abstract representation of the chords being used" - as in Claude Debussy's Première Arabesque.

In the medieval era, early Christian hymns featured organum (which used the simultaneous perfect intervals of a fourth, a fifth, and an octave), with chord progressions and harmony an incidental result of the emphasis on melodic lines during the medieval and then Renaissance (15-17th centuries).

The Baroque period, the 17th and 18th centuries, began to feature the major and minor scale based tonal system and harmony, including chord progressions and circle progressions. It was in the Baroque period that the accompaniment of melodies with chords was developed, as in figured bass, and the familiar cadences (perfect authentic, etc.). In the Renaissance, "certain dissonant sonorities that suggest the dominant seventh occurred with some frequency." In the Baroque period the dominant seventh proper was introduced and it was in constant use in the Classical and Romantic periods. The leading-tone seventh appeared in the Baroque period and remains in use. Nondominant seventh chords began to be used in the Baroque period, became frequent in the Classical period, gave way to altered dominants in the Romantic period, and underwent a resurgence in the Post-Romantic and Impressionistic period.

The Romantic period, the 19th century, featured increased chromaticism. Secondary dominants began to be used in the Baroque, becoming very common in the Romantic period. Many contemporary popular Western genres continue to be founded in simple diatonic harmony, though far from universally: notable exceptions include the music of film scores, which often use chromatic, atonal or post-tonal harmony, and modern jazz (especially circa 1960), in which chords may include up to seven notes (and occasionally more).

Triads consist of three notes; the "root" or "first" note, the "third" and the "fifth". For example the C major scale consists of the notes C D E F G A B: a triad can be constructed on any note of such a major scale, and all are minor or major except the triad on the seventh or leading-tone, which is a diminished chord. A triad formed using the note C itself consists of C (the root note), E (the third note of the scale) and G (the fifth note of the scale). The interval from C to E is of four semitones, a major third, and so this triad is called C Major. A triad formed upon the same scale but with D as the root note, D (root), F (third), A (fifth), on the other hand, has only three semitones between the root and third and is called D minor, a minor triad.