The term "tonality" is used in both a specific and general sense. In 1810 French musicologist Alexandre-Étienne Choron (1771-1834) defined tonality in the way it is used today, as an organization of harmonic triads around a focal major or minor triad, the tonic, with the subdominant on the fourth scale degree, driving to the dominant on the fifth, followed by a resolution to the tonic. A variety of metaphors, such as "gravitational pull", have subsequently been used to describe the perceptual forces at play in this arrangement.Tonality gives the ear a "center," providing a context in which melody and harmony have meaning.
The three chords of the tonic, subdominant, and dominant provide a rudimentary harmonization of most tunes constructed from a diatonic scale. Since the early 17th century they have come to replace an older melodic/harmonic approach based on the twelve church modes. Today, the concept of tonality includes a complex syntax of chords surrounding a referential tonic chord.
"Tonality" has been used in wider, less useful senses, too, to describe pitch organizations around a referential pitch center, such as the scale system in North Indian classical music, and even to describe the oranization of highly atonal music (such as"twelve-tone tonality", the technique devised by the composer George Perle).
Notes that do not belong to a chord, or chords that do not belong to the key, create tension and require resolution; this was explored i the chromatic music of J. S. Bach in the 18th century and that of Richard Wagner in the 19th, culminating in Wagner's operas Tristan and Isolde (1865) and Parsifal (1882). During the first decades of the 20th century, a notion arose that the constant increase in complexity would result in a total breakdown of the system in favor of atonality. However, tonality continues to dominate music today, particularly in many genres of popular music, but also in neo-romantic music.