Standard Progressions (with audio!)
I'm going to continue talking about chord progressions by providing visual & audio examples of standard paradigms. (Note: I'll use the word 'chord' and 'triad' interchangeably for now.) Be confident that the application of these examples is practically universal; exceptions are rarely found in Western Music. As a result (and as we've covered earlier), Music that employs these progressions may be understood to provide a signifying function that connects or refers to the corpus of Western Music. Conversely, Music that avoids or mutates these examples significantly may provide different kinds of signification. (More on that later.)
Remember that proper understanding of the "Musical Language" (and thus, musical cognition) requires more insight than simply labelling or hearing individual chords. Being able to understand how chords move from one to the other is important to comprehension. Just as the meaning carried by spoken language is contingent upon the ordering of words in a sentence, the ordering of chords in a progression is also meaningful.
The Dominance of the Dominant
The dominant chord (that is to say, the triad built on the fifth scale degree) is important for many reasons, but here are few:
- It is built on the fifth scale degree (besides the tonic, it is the second pitch in the overtone series), a perfect fifth above the tonic (an acoustic phenomenon),
- The dominant chord is a major triad (besides the tonic chord, only the dominant and subdominant are major), and
- It contains the leading tone (7) pitch, which tends to "lead" into the tonic key/chord.
Although there are exceptions, most music pivots on the relationship between the tonic chord (I) and the dominant (V) chord. Most pieces begin and end with the tonic chord, and most of the chord movements/progressions within will be between the tonic and dominant. Many phrases will begin on the tonic and end with the dominant, or begin on the dominant and end on the tonic.
Structurally speaking, most chord progressions can be reduced to a I-V-I relationship, and in fact, most compositions perform a large-scale "working out" of a I-V-I progression. This constitutes a "language," with its own rules of grammar.
Let's explore a way this can be seen and heard.
Example 1: The Essential I-V-I motion
The metaphor of motion is inextricably bound with how we hear and understand chord progressions. We speak of a "motion away from the tonic" and a "motion toward the tonic." All tonal Music, sooner or later, will progress (move) away from the tonic chord to the dominant, and back again. It performs this journey on a microscopic (that is to say, from one chord to the next) as well as a macroscopic (as in the large formal organization of a symphony) level.
This example shows the underpinning, essential chord progression from I-V-I. Hear the example here: Example1. Does it sound familiar? It should, for it is nearly ubiquitous in our Musical vocabulary.
Example 2: The Sub- or Pre-Dominant
Chords build on the second scale degree (ii) or the fourth (IV) are most often used to "prepare" or "lead into" the dominant (V) chord. Chords that perform this function are regarded (and heard) as being structurally less important than the essential I-V-I motion. Progressions that employ these chords always do so in a "decorative" way, adding interest and variety to the underlying I-V-I motion:
Here we see that the IV and ii triads can be interchanged (as they both perform a "pre-dominant" function) and both add interest and motion toward the dominant chord.
Compare this example to the previous one by listening here: Example2. Note the additional IV chord that proceeds the V, creating additional interest. This too, should also be a familiar progression.
Example 3: Adding the Submediant, or vi
In the same way the ii or IV chord proceeds toward the dominant, the vi (or 'submediant') chord can progress toward the subdominant.
Again, the vi, ii, and IV chords ultimately lead to the dominant--the essential, underlying I-V-I progression is intact; the additional chords serve as decorations or embellishments.
Listen here: Example3. Again, hear the progression and understand that the vi and IV chords are leading to the dominant, a progression that underpins all of these examples (I-V-I). You find it familiar as it's used heavily in many situations. Compare this progression to one common example, "Heart and soul," here: http://www.youtube.com/watch?v=ibfJsyx6N_U
What does this mean?
Chord analysis is more than simply labelling vertical structures. The order in which chords are heard forms a type of language with its own grammar; the "story" being told by a piece of music depends largely on the order in which chords are played.
The structural basis for most Music is the tonic-dominant progression, a motion from the tonic (I) chord to the (V) and back again. Other triads may appear, but their role is subsidiary; they are present to add interest and tension. Ultimately, they progress to the dominant, which returns to the tonic.