CHORD (from the Greek word chord', a string of gut). 1. In music, the simultaneous and harmonious union of different sounds, at first intuitively recognized by the ear, and after ward reduced to a science by the invention of the laws or rules of harmony. Chords may consist of from two to five parts. Absolute chords of two parts are produced only by thirds or sevenths. Chords of more than two parts are either fundamental chords or inversions of them and are divided into concords and dis cords. The union of sounds in all chords will be found, on analyzing their component parts, to be an admixture of major and minor thirds. The common chord of Trais harmonica perfecto is the basis of all harmony and consists of a base note or prime, with its third and fifth above. These three sounds are the distance of a third from each other. When the lowest third is the greater third, as above, the chord is a major chord; but when the lowest third is the lesser, the chord is called a minor chord. A chord of two minor thirds combined is called diminished, as the interval from the lowest note to the highest is less than a perfect fifth; the common chord admits of two inversions, ac cording as one or other of its notes is made the base, or lowest note of the chord.
By adding another third above the common chord, a chord of four parts is produced, which is called the chord of the seventh, because the highest note is a seventh above the base. When
the chord of the seventh is produced on the fifth of the scale it is then called the dominant seventh, which is the most perfect species of the chord. It then consists of a major third, perfect fifth and seventh, the minor, which is the next harmonic produced by nature above the fifth. The chord of the seventh may be formed also on any of the notes of the major or minor scale taken as a bass note, which produces the varieties of major, minor and diminished seventh. The chord of the seventh admits of three inversions, according as the notes above the fundamental note are used as bass notes. From its nature it requires a resolution and is therefore always followed by a common chord, whose fundamental bass is a fifth below that of the seventh.
2. In peometry, a chord is the straight line which joins the two extremities of the arc of a curve; so called from the resemblance which the arc and chord together have to a bow and its string, the chord representing the string. The chord of a circular arc is obtained by multiplying the radius by twice the sine of half the angle which the arc subtends at the centre.