AP Music Theory part-writing guide
Plan the harmony, frame the outer voices, then check the same seven things.
Most part-writing points are lost to a short list of repeatable errors. Plan the cadence first, write outer voices before inner ones, and audit spacing, doubling, parallels, and resolution in a fixed order.
Short answer
Assign Roman numerals and the cadence before notating anything, write bass and soprano first, then check parallels, spacing, crossing, range, doubling, tendency-tone resolution, and notation in that order.
Plan the harmony before you write a single inner voice
Part-writing errors are usually planning errors that surfaced late. Before notating anything, read the whole bass line or melody, mark the cadence, and decide the harmonic rhythm. A phrase whose cadence is chosen last tends to arrive at an unusable chord.
Write the outer voices first. A bass line and a soprano that already move well against each other leave far fewer traps for the alto and tenor, because most forbidden parallels and spacing problems are between the voices you have not written yet.
- 01Identify the key, then mark the cadence and any modulation target.
- 02Assign Roman numerals across the phrase before notating pitches.
- 03Set the outer-voice frame and check its intervals for parallels.
- 04Fill alto and tenor within range and spacing limits.
- 05Run a final resolution pass on every tendency tone and seventh.
The checklist that catches most lost points
Most deductions come from a small, repeatable set of problems. Checking them in a fixed order is faster and more reliable than rereading the whole answer hoping something looks wrong.
- 01Parallel fifths and octaves between any pair of voices, including bass to alto.
- 02Spacing: more than an octave between soprano and alto, or alto and tenor.
- 03Voice crossing and overlap between adjacent voices.
- 04Range: every voice inside its stated limit, at the phrase edges too.
- 05Doubling: usually the root; never a leading tone or an altered tone.
- 06Resolution: leading tone to tonic, chordal sevenths down by step.
- 07Notation: correct clefs, stem directions, accidentals, and the key signature applied consistently.
Figured bass and melody harmonization fail differently
In figured-bass realization the harmony is given. Your job is to read the figures accurately — including inversion and any accidental applied to the figure — and produce clean voice leading above the supplied bass. The failure mode is misread figures propagating into the inner voices.
In melody harmonization you choose the harmony. That freedom is where answers go wrong: an unclear cadence, a bass line that moves in parallel with the melody, or a progression that keeps restating tonic without a functional predominant. Commit to a functional plan first, then compose the bass line to support it.
Retest the specific rule you broke
"Study voice leading" is not a practice task. "Write four phrases where the chordal seventh has to resolve down by step" is. Read the scored evidence, name the single rule that failed, and drill that rule on new material.
MIDI Mind shows which rule was violated and where, so the retest can be narrow. A fresh exercise on the same rule tells you whether the correction transferred; repeating the exercise you just corrected mostly tests memory.
Common questions
What are the most common AP Music Theory part-writing mistakes?
Parallel fifths and octaves, spacing greater than an octave between adjacent upper voices, doubled leading tones, unresolved chordal sevenths, and voices written outside their stated ranges. Checking those six in a fixed order catches most lost points.
Should you write inner voices or outer voices first?
Outer voices first. Bass and soprano determine most of the parallel-motion and spacing risk; once that frame is clean, the alto and tenor have far fewer valid-but-wrong options.
How is figured-bass realization different from harmonizing a melody?
Figured bass supplies the harmony, so accuracy in reading the figures and clean voice leading are what is assessed. Harmonizing a melody requires you to choose the progression as well, which means cadence planning and a functional bass line become part of the answer.
How do you practise part writing without a teacher marking it?
Use practice that states which rule was broken and where, rather than only a score. MIDI Mind generates figured-bass and harmonization exercises and returns rule-level feedback, so you can drill one specific voice-leading decision and retest it on new material.
Related AP Music Theory resources
Place written free response inside a balanced diagnostic cycle.
Hear the progressions you are asked to write out in four parts.
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