User:Rheostatik/Harmonic 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.

Chord progressions are used to create movement within a piece of music, offering a shift of level or simultaneity succession essential to harmony. Music is not a static art form like sculpture; it exists within a time frame and people respond to this psychologically by their need for a start and end with a central tonality. Music creates this expectation regardless whether it is a melody line or a chord progression. Chord changes generally occur on an accented beat and by doing so creates a sense of rhythm, meter and musical form for a piece of music, while also delineating bars, phrases and sections.

Nomenclature
In music theory, scale degrees are typically represented with Arabic numerals, often modified with a caret or circumflex ( $$\hat 1, \hat 3, \hat 5$$ would be the notes C, E and G in the key of C), whereas the triads that have these degrees as their roots are often identified by Roman numerals. Upper-case Roman numerals indicate major triads while lower-case Roman numerals indicate minor triads, as the following chart illustrates. Lower-case Roman numerals with a degree symbol indicate diminished triads. For example, in the major mode, the triad built on the seventh scale degree ( $$\hat 7$$) is diminished (vii°).

Triads may be constructed using any degree of a scale as the root, and diatonic triads consist only of notes belonging to the scale. That is, if a passage is in G major, most of the chords contain only notes found in the G major scale. Subsequently, a chord's function changes according to the scale from which it is derived. A "D minor" chord will be the tonic chord ( i ) when built from the scale of D minor. It will be the super-tonic chord ( ii ) if it is derived from the scale of C major, or the sub-mediant ( vi ) chord if derived from the scale of F major.

This also means that a D minor chord does not appear at all in some keys, such as A Major, due to the presence of an F# in the key signature. This can be rectified by temporarily lowering the sixth scale degree ( $$\hat 6$$) from F# to F♮, resulting in a minor subdominant chord ( iv ) in a major scale, which, depending on the overall chord progression, can be considered aesthetically pleasing (see altered chord).

Circle of Fifths
One of the most fundamental aspects in Western music is the Circle of Fifths, which consists of roots related by ascending 5ths (and descending 4ths).