A chord progression is an ordered series of chords that creates harmonic motion toward a goal (usually a cadence). In AP Music Theory, you analyze and write progressions using Roman numerals and 18th-century voice-leading rules, including how passing, pedal, and arpeggiated 6/4 chords fit inside them.
A chord progression is a sequence of chords moving in a purposeful order. It is the harmonic skeleton of a piece. Each chord has a job (tonic, predominant, or dominant function), and a good progression moves through those jobs in a logical direction, usually landing on a cadence. Think of it like a sentence. Individual chords are words, but the progression is the grammar that makes them mean something.
In AP Music Theory, you don't just name chords. You explain how they connect. Unit 5 (Harmony and Voice Leading II) is literally subtitled "Chord Progressions and Predominant Function," and Topic 5.7 zooms in on a tricky case. Second-inversion (⁶₄) chords are unstable, so they can't just appear anywhere in a progression. They have to be embellishments. The passing ⁶₄ harmonizes a bass passing tone between two chords, the pedal (or neighboring) ⁶₄ decorates a root-position chord while the bass holds still, and the arpeggiated ⁶₄ shows up when the bass arpeggiates through the triad. Each one decorates a progression without changing its underlying harmonic function.
Chord progressions are the organizing idea of Unit 5, and Topic 5.7 tests whether you can handle the exceptions. Learning objective AP Music Theory 5.7.A asks you to describe which type of ⁶₄ chord appears in notated music, and AP Music Theory 5.7.B asks you to identify and apply 18th-century voice-leading procedures for passing, pedal (neighboring), and arpeggiated ⁶₄ chords through score analysis, error detection, writing exercises, and contextual listening. That means you need to see a ⁶₄ chord inside a progression and instantly know its job. Is the bass passing by step (PIT-2.L.2)? Is the bass frozen while upper voices neighbor up and back (PIT-2.L.1)? Is the bass arpeggiating the same triad (PIT-2.L.3)? Progressions also drive the part-writing FRQs, where you realize a figured bass or harmonize a melody, and a wrong ⁶₄ usage is an easy way to lose points.
Keep studying AP Music Theory Unit 5
Visual cheatsheet
view galleryPassing six-four (Unit 5)
The passing ⁶₄ is a progression's smoothing device. It harmonizes the middle note of a three-note bass scale fragment so the bass can walk by step instead of leaping. When you part-write it, double the fifth of the ⁶₄ chord and keep every voice moving stepwise (PIT-4.F.1).
Neighboring six-four (Unit 5)
The pedal (neighboring) ⁶₄ happens when the bass sits still and the third and fifth of a root-position triad step up to their upper neighbors and come back. The progression doesn't actually move; the ⁶₄ is decoration on a weak beat, not a new functional chord.
Cadence (Units 4-7)
A cadence is the destination a progression travels toward. Every progression you analyze or write on the exam should aim at a cadence, and the cadential ⁶₄ (covered earlier in Unit 5) is the one ⁶₄ chord that lives right at that arrival point, decorating the dominant.
Harmony (Units 4-7)
Harmony is the broad study of how chords work; a chord progression is harmony in motion. Once you can label a single chord with a Roman numeral, progressions are the next step. They tell you whether that chord is functioning as tonic, predominant, or dominant in context.
Expect multiple-choice questions that play a short excerpt or show a score and ask you to classify a ⁶₄ chord within a progression. A classic setup gives you a stationary bass note (say, F held for three beats in F Major) while upper voices move away and back, and asks what type of chord the middle sonority is. The answer is a pedal ⁶₄. Other stems ask which voice stays constant in a pedal ⁶₄ (the bass) or which progression breaks voice-leading rules. On the FRQs, progressions show up in figured-bass realization and melody harmonization. You have to choose chords that imply a logical progression (PIT-4.F.4 reminds you that adding a bass to a soprano implies a harmonic progression) and handle any ⁶₄ chords correctly, doubling the right note and using stepwise motion. Error-detection questions also love ⁶₄ misuse, like treating a passing ⁶₄ as if it had real predominant or dominant function when it's really just harmonizing a bass passing tone.
A chord progression is the whole harmonic journey; a cadence is just the ending. Students often use the words interchangeably, but on the exam they're tested differently. Progressions test your ability to track function from chord to chord, while cadences test how a phrase closes (authentic, half, plagal, deceptive). A cadence is technically a short progression, but not every progression is a cadence.
A chord progression is an ordered sequence of chords that moves through tonic, predominant, and dominant functions toward a cadence.
Second-inversion (⁶₄) chords are unstable, so in 18th-century style they only appear in progressions as embellishments, not as functional chords on their own.
A passing ⁶₄ harmonizes a bass passing tone in a three-note stepwise bass line, and you should double its fifth with all voices moving by step.
A pedal (neighboring) ⁶₄ keeps the bass stationary while the third and fifth of a root-position triad step up to upper neighbors and return, usually on a weak beat.
An arpeggiated ⁶₄ happens when the bass arpeggiates through its own triad while the upper three voices stay put.
When you add a bass line to a melody on the part-writing FRQ, your note choices imply a harmonic progression, so plan the progression before you write the voices.
It's a series of chords arranged in a purposeful order, labeled with Roman numerals, that moves through tonic, predominant, and dominant functions toward a cadence. Unit 5 of the course is built around progressions and how voice leading connects the chords inside them.
No. Passing, pedal, and arpeggiated ⁶₄ chords are embellishments, not functional chords like a real predominant or dominant. A passing ⁶₄, for example, just harmonizes a bass passing tone on a weak beat without changing where the progression is headed.
A progression is the full sequence of chords; a cadence is only the closing gesture at the end of a phrase. Every cadence is a tiny progression, but a progression can run for many measures before it ever reaches a cadence.
Watch the bass. In a passing ⁶₄ the bass moves by step through a three-note ascending or descending line, while in a pedal ⁶₄ the bass holds the same note and the upper voices neighbor up and back. Both usually land on weak beats.
The bass. In a pedal (neighboring) ⁶₄, the bass remains stationary while the third and fifth of the root-position triad are embellished by their upper neighbor tones, which is exactly how the CED defines it (PIT-2.L.1).
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