AP Music Theory: Composition

Composition in AP Music Theory is not about free-form artistic expression; it is the rigorous application of theoretical rules to create stylistically coherent music, primarily in the tradition of Common Practice Period harmony. Your success on the exam’s free-response questions hinges on demonstrating control over musical materials through disciplined part-writing and melodic design. Mastering these skills transforms abstract knowledge of chords and scales into the ability to construct convincing musical phrases.

The Foundation: Four-Part Voice Leading and Rules

All composition tasks on the AP exam are built upon the framework of four-part voice leading, which models the standard soprano, alto, tenor, and bass (SATB) texture of chorales and hymns. This texture provides a clear container for applying harmonic rules. Proper voice leading ensures that each of the four lines is singable and independent while moving smoothly from chord to chord.

The core rules govern the motion of individual voices and their interactions. You must avoid parallel fifths and parallel octaves (where two voices move in identical motion to a perfect fifth or octave), as they destroy the independence of the voices. Resolve the leading tone (scale degree 7) upward by step to the tonic, especially in outer voices. The chordal seventh, if present, must resolve down by step. Furthermore, approach all perfect intervals (unisons, fourths, fifths, octaves) carefully; avoid leaping into them in similar motion between the outer voices (soprano and bass), a rule known as direct or hidden fifths/octaves. Spacing is also critical: the distance between soprano and alto, and alto and tenor, should not exceed an octave, while the tenor-to-bass distance can be wider.

Constructing Coherent Chord Progressions

Harmonization is not just a series of correct chords; it is about creating a logical chord progression that establishes and confirms a tonal center. Your progression should follow the fundamental tonal pull: tonic (I) -> predominant (ii or IV) -> dominant (V or viio) -> tonic (I). This tonic-predominant-dominant-tonic model is the essential backbone. Within this, use root position chords for stability, especially at phrase beginnings and cadences. First-inversion (6) chords are excellent for bass line mobility. The cadence—the harmonic goal of a phrase—is your primary punctuation. The authentic cadence (V-I) is a period, the plagal cadence (IV-I) is an "amen," and the half cadence (ending on V) is a question mark.

When harmonizing a given melody, your first step is to identify the implied harmonic rhythm (how often chords change) and locate the cadence points. Then, work backwards from the cadence, choosing chords that not only fit the melody notes but also create a strong, logical bass line that often moves in contrary or oblique motion to the soprano.

The Art of Melodic Embellishment: Non-Chord Tones

Non-chord tones (NCTs) are pitches that do not belong to the underlying harmony but are used to embellish and connect the chord tones. They make music fluid and expressive. You must identify and use them correctly. A passing tone (PT) fills in a stepwise leap between two chord tones. A neighbor tone (NT) steps away from a chord tone and back. An appoggiatura (APP) is a leap into the dissonance, then a step down to resolve. An escape tone (ET) is a step up from a chord tone, then a leap down to resolve. Suspensions (SUS), crucial for cadences, involve holding a note from the previous chord, creating a dissonance, then resolving down by step.

In your harmonizations, NCTs primarily occur in the upper three voices. They are always approached and left according to specific rules. Using them appropriately demonstrates a sophisticated understanding of line versus harmony and is essential for earning high marks on the exam.

Modulating to New Keys

Modulation is the process of moving from the home key (tonic) to a new, closely related key. On the AP exam, you are most often asked to modulate to the dominant (from C major to G major) or the relative minor (from C major to A minor). The most common and clearly audible technique is pivot chord modulation. Here, a chord that is diatonic (naturally occurring) in both the original key and the destination key is used as the turning point. For example, in C major, the ii chord (D minor) is also the vi chord in the new key of G major. You would write: C: I - ii | G: vi - V - I. After the pivot, you must include a strong authentic cadence (V-I) in the new key to confirm the modulation conclusively.

Realizing Figured Bass

Figured bass realization is a direct test of your harmonic grammar. The given bass line and figures (numbers like 6, 6/4, 7) tell you exactly which chords to write in which inversions. Your job is to compose the three upper voices correctly above this bass. Treat the bass note as given and immutable. The figures indicate the intervals above that bass note. For example, a "6" indicates a first-inversion chord (the third of the chord is in the bass), requiring a sixth and a third above the bass. You must apply all standard voice-leading rules to these upper voices. This task is purely mechanical but requires flawless execution; it proves you understand the vertical alignment of harmony.

Principles of Melodic Composition

When asked to compose a melody, you are applying the rules in reverse. A good melody has a clear relationship with an underlying harmonic progression, even if not explicitly written. Compose with a strong sense of tonality, using scale degrees 1, 3, and 5 as primary structural pillars. Create a coherent contour—a shape that rises, peaks, and falls. Use primarily stepwise motion with occasional leaps, and always balance a leap with stepwise motion in the opposite direction. Incorporate appropriate non-chord tones for fluidity. Most importantly, your melody must conclude with a convincing cadence, typically aligning with a V-I or V-i progression in the implied harmony. Rhythmic variety and motivic development (repeating and varying a small idea) will elevate your melody beyond the mundane.

Common Pitfalls

1. Ignoring the Cadence: The most common error is failing to write a clear, standard cadence at the required point. An ambiguous ending or a weak progression (like I-V-vi) will immediately lower your score. Always end phrases with strong, textbook cadences (V-I, iv-i, etc.).

1. Poor Doubling in Inversions: In root position major and minor triads, double the root. In first-inversion chords, double the soprano (which is often the root or fifth) or the bass note (the third) to ensure stability. A frequent mistake is doubling the leading tone or the chordal seventh, which creates glaring voice-leading errors.

1. Misidentifying Non-Chord Tones: Students often mislabel a passing tone as a neighbor tone or fail to see a suspension. Remember the approach and resolution rules: a suspension must be prepared (held over), suspended, and resolved down. An appoggiatura is approached by leap. Confusing these breaks the contrapuntal logic.

1. Forgetting to Confirm a Modulation: Simply using a pivot chord is not enough. You must write a full authentic cadence (V-I) in the new key after the pivot. Ending the modulation section on anything other than a tonic chord in the new key leaves the listener—and the grader—uncertain about where you've landed.

Summary

• AP composition is applied theory: Your goal is to demonstrate mastery of Common Practice Period rules through part-writing and melodic creation, not personal artistic style.
• Voice leading is non-negotiable: Adherence to rules regarding parallel motion, spacing, and tendency tones forms the foundation of every free-response answer.
• Harmony follows a logical path: Construct progressions using the tonic-predominant-dominant-tonic model and articulate phrases with strong, conventional cadences.
• Non-chord tones and modulation are advanced requirements: Correct use of NCTs and clear pivot-chord modulations are key differentiators for a high score.
• Every task is interconnected: The skills for figured bass realization directly inform your ability to harmonize a melody, and melodic composition requires an implicit understanding of the harmony it outlines.