Chord progression

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 and that is based upon a succession of root relationships. 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 level that is essential to many musical traditions. 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. This is known as harmonic rhythm.

Basics

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 of its own chord. A chord built upon the note A is an A chord of some type (major/minor/diminished, etc.) The harmonic function of any particular chord depends on the context of the particular chord progression in which it is found. (See Diatonic function)