The term "chord" is well known to every professional musician. A special musical discipline, which is called "harmony", deals with the study of the types of chords.
It is customary to call a chord a generally accepted musical unit, which is a combination of three notes, the interval between which is a third, that is, three semitones. This definition of the term appeared in 1732 thanks to the German composer and music theorist Johann Gottfried Walter. It was he who suggested replacing the then wider meaning of the chord as a set of simultaneously sounding notes with the one that is known to modern musicians. In addition to the classical triads, more complex chords are often found, which can contain four, five or seven sounds. The last two, called non-chords and undecima chords, respectively, are not very common, especially in relation to simple guitar compositions. The most common among complex chords are combinations of four sounds - the so-called seventh chords. The three root notes are one third apart from each other, just like regular triads, but the fourth sound is played a seventh from the third, and each chord has a so-called root note. It is customary to call the lowest note of the chord. The root also gives the name to the entire chord. So, if the triad is represented by the notes "C", "E" and "G" of one octave, then the chord will be called "C". At the end of the nineteenth century, some musicians attempted to replace the usual tertz chords with quarts, the interval between the notes in which was not three, but four steps. However, this change did not gain widespread popularity. Nevertheless, today in music, dissonances, as well as so-called mixed chords, which differ in their structure from the classical ones, are often used to add color and personality to a piece.
