The Basic Phrase Model: Tonic and Dominant Chords
The Basic Phrase Model
The diagram above models the essential harmonic elements and their order within a complete musical phrase in tonal music. The tonic and dominant chords are the harmonic “pillars” on which tonal music is based. A tonic chord normally begins a piece of music (although introductory material may precede it). A phrase of music ends with a cadence. A complete musical thought ends conclusively by moving from the dominant chord to the tonic chord, both in root position. This is an authentic cadence. It is also possible to stop short of the final tonic and end inconclusively on the dominant chord. This is a half cadence.
We understand the significance of a half cadence against the backdrop of the basic phrase model. The model shows how a phrase should begin and end if it is to be a complete musical thought. We sense the incompleteness of a phrase that stops shy of the final tonic and cadences on the penultimate element of the model. The lack of full closure in a half cadence becomes a basic compositional resource: Closure is denied in one phrase, only to be satisfied in a subsequent phrase.
An Example: Beethoven, Violin Sonata in Op. 12, No. 1
Locate the elements of the basic phrase model in the excerpt below. What elements of the basic phrase model are missing?
Beethoven, Violin Sonata in Op. 12, No. 1, movement 3
This phrase is in D major. It begins on tonic and ends on the dominant, which creates a half cadence in measure 4. Our expectation of closure is thwarted as the phrase does not conclude with the final element of the basic phrase model, the tonic. Much like a television drama that ends an episode with a “cliff-hanger” and makes us wait for the next episode to bring resolution, we must wait for the next phrase to tie up the loose ends.
The next phrase, shown below, does indeed complete the phrase model. The last two chords of the second phrase, root-position V7 and I chords, create an authentic cadence. There are two kinds of authentic cadences, depending on the scale degree in the main melody above the bass. The cadence in the example below is a perfect authentic cadence because it ends with scale degree one in the uppermost melody. Imperfect authentic cadences typically end with scale degree three in the uppermost melody. This is the main kind of imperfect cadence; we broaden the definition to include any authentic cadence that does not qualify as a perfect authentic cadence (as in those fairly rare instances when scale degree five is in the main upper melody or when the dominant is inverted).
Notice that there is a pick-up chord, an inversion of V7, at the very beginning of the second phrase. This does not prevent the I6 chord that appears on the first downbeat of the phrase from serving as the opening tonic, the first element of the basic phrase model.
Some Foundational Concepts
Writing Music Comprised of Tonic and Dominant Chords
Resolving the Tendency Tones in V7 Chords
There are two tendency tones in a V7 chord:
1. The leading tone (^7) resolves up by (half) step.
Exception: When it is in an inner part, the leading tone has the freedom to leap down a third to scale degree 5.
2. The chordal seventh (^4) resolves down by step.
Exception: When writing the chords I-V43-I6, the uppermost notes in each chord often moves up like this: ^3-4-5, even though the chordal seventh (^4) goes up instead of down.
Perhaps this is because the outer parts move in parallel thirds, and the consonance and ascending motion of the counterpoint overrules the dissonance of ^4 with the root and third of the chord.