Chord Progression : The Basics

A chord progression (or harmonic progression) is a series of musical chords, or chord changes that "aims for a definite goal" of establishing (or contradicting) a tonality founded on a key, root or tonic chord. Chords and chord theory are generally known as harmony.

A chord progression can be thought of as a harmonic simultaneity succession: it offers an ongoing shift of levelOceania and South/West Africa. A change of chord, or "chord change", generally occurs on an accented beat, so that chord progressions may contribute significantly to the rhythm, meter and musical form of a piece, delineating bars, phrases and sections. that is essential to the music of Europe (at least since 1600),

A chord may be built upon any note of a musical scale, therefore a seven-note scale allows seven basic chords, each degree of the scale becoming the "root" or "tonic" of its own chord. A chord built upon the note A is an A chord: however, since any progression may be played in any key, the fundamentals of harmony are best grasped by numbering the chords according to the step of the scale they are built upon, upwards from the key-note. The structural meaning of a harmony depends exclusively upon the degree of the scale.

Any major scale gives three major triads that together include, and so can harmonize, every note of that scale. They are based on the first, fourth, and fifth scale degrees (the tonic, subdominant and dominant).

Diminished Chords

The same scale also provides three relative minor chords, one related to each of the three major chords. These are based upon the sixth, second and third degrees of the major scale and stand in the same relationship to one another as do the three majors, so that they may be viewed as the first, fourth and fifth degrees of the relative minor key. Apart from these six common chords there will be one step of the scale that gives a diminished chord.

In addition, extra notes may be added to any chord. If these notes are also selected from the original scale the harmony remains diatonic. If new chromatic intervals are introduced then a change of scale or modulation occurs, which may bring the sense of a change of tonal center. This in turn may lead to a resolution back to the original key, so that the entire sequence of chords helps create an extended musical form.  

Although all this allows for a large number of possible progressions (depending upon the length of the progression), in practice progressions are often limited to a few bars' length and certain progressions are favored above others: there is a certain amount of fashion in this and a chord progression may even define an entire genre.

In western classical notation chords built on the scale are numbered with Roman numerals. A D chord will be figured I in the key of D, for example, but IV in the key of A. Minor chords are signified by lower case Roman, so that D minor in the key of C would be written ii. Other forms of chord notation have been devised, from figured bass to the chord chart. These usually allow or even require a certain amount of improvisation. [source : Basic Chord Progression]