� Circle Progressions
Adjacent chord roots in ascending fourth or descending fifth relationship (I-IV-viio-iii-vi-ii-V-I) are the strongest and most common type of chord progression.
Ascending Fifth and Descending Fourth Progressions
Provide relief from the constant motion toward tonic. The most frequent application is the half cadence (I-V)
Ascending Second Progressions
Are often used to prepare a shift from the circle progression I-IV to another circle progression, V-I. The resulting progression I-IV-V-I.
Descending Third Progressions
Provide contrast and facilitate change from one circle progression to another. Descending third progressions are often used in harmonic movement away from the tonic (I-vi)
or in a longer chord series (I-vi-IV-ii).
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Tonic Function: Phrases
Often open with a mixture of circle and non-circle progressions and close with a strong succession of circle progressions.
Tonic Function: The Leading Tone Harmony
Most often considered dominant harmony since the triad contains the third, fifth, and seventh of the dominant seventh chord. For this reason, the leading tone triad usually progresses to the tonic in an ascending second relationship, and is a weaker form
Tonic Function: Second-Inversion Tonic Triad
Especially in the cadence formula I6/4-V-I reflects little of the stable quality normally associated with the tonic function and should be considered a decoration of the V chord.
Harmonic Rhythm
The frequency of harmonic changes in a composition and has the function of defining or confirming the prevailing meter of a composition.
Even when the harmonic rhythm is faster than one chord per measure, chord changes will usually coincide with each downbeat.
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A chorale or hymn tune traditionally uses one chord to each melody note, whereas folk tunes often have
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one chord for each measure.
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Principles for Choosing Chords
1. You must use half (I-V, IV-V, or ii-V) or authentic (V-I) cadences for the final two notes of each phrase.
2. You should use circle progression throughout in each phrase. Circle progressions are more often longer and more abundant near the cadence than at the beginning of the phrase.
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3. Harmonize each melody note with one chord. It is possible to repeat chords occasionally, but
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adjacent repeated chords are usually in different positions to provide melodic motion in the bass.
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4. Employ first-inversion chords and non-harmonic tones to make a smoother (stepwise) bass melody.
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5. Shape the bass line carefully to make it a singable melodic line.
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6. Avoid overuse of ascending third and descending second progressions.
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