AP Music Theory — Cheatsheet
Formulas, exam-day tips, and key terms on one page.
Formulas & relationships
Major scale step pattern
W – W – H – W – W – W – H (do re mi fa sol la ti do)
Half steps fall between degrees 3–4 (mi–fa) and 7–8 (ti–do). Every major scale, in any key, uses exactly this pattern.
Reading a compound time signature
beats = (top number) ÷ 3 · beat unit = dotted note · division = 3
For 6/8: 6 ÷ 3 = 2 beats (duple), each beat a dotted quarter dividing into three eighths. For 9/8: three beats; for 12/8: four beats.
Relative and parallel relationships
relative major = up a minor third from minor tonic · parallel = same tonic, different mode
Relative keys share a signature (A minor ↔ C major). Parallel minor lowers the major scale’s 3rd, 6th, and 7th degrees (C major → C minor: E♭, A♭, B♭).
Texture at a glance
monophony = 1 line · homophony = 1 melody + accompaniment · polyphony = 2+ independent lines
Count the independent melodic lines and note whether accompaniment is subordinate (homophony) or of equal interest (polyphony).
Half steps per interval quality
m2=1 · M2=2 · m3=3 · M3=4 · P4=5 · TT=6 · P5=7 · m6=8 · M6=9 · m7=10 · M7=11 · P8=12
Count half steps between the two pitches, then match the number and the letter-name size to this table. Inversions of any pair sum to 12 half steps (and size numbers sum to 9).
Chord-quality recipes
Major=M3+m3 · minor=m3+M3 · dim=m3+m3 · aug=M3+M3 || seventh chord = triad + (M7, m7, or d7)
Read a triad from its two stacked thirds; add the top third to get the seventh. Figured bass for triads: root=(blank), first inv=6, second inv=6/4.
Diatonic triads and function in major
I ii iii IV V vi vii° → T: I, vi · PD: ii, IV · D: V, vii°
Case shows quality (I major, ii minor, vii° diminished). Functional flow is T → PD → D → T; the dominant resolves the leading tone up to the tonic.
Cadence chord templates
PAC/IAC: V(7) → I · HC: … → V · DC: V → vi · PC: IV → I
PAC additionally requires both chords in root position and the soprano ending on do. Break either condition and V–I becomes an IAC.
Figured-bass inversion symbols
triad: (blank)=root · 6=first · 6/4=second || 7th chord: 7=root · 6/5=first · 4/3=second · 4/2=third
The figures count intervals above the bass. The bass note identifies the inversion: root, third, fifth, or seventh of the chord in the bass, respectively.
Predominant templates
ii(6) or IV → V(7) → I · ii7 in C = D–F–A–C (2–4–6–1)
Predominants (ii, IV, and their sevenths) prepare the dominant. ii → V is a strong descending-fifth root motion; IV → V needs contrary motion to avoid parallels.
Classifying an NCT by its motion
PT: step–step (same dir) · NT: step–step (return) · SUS: hold–step down · APP: leap in–step out · ET: step in–leap out · ANT: early chord tone
Ask two questions: how is the tone approached, and how is it left? The pair of answers (and the direction) names every non-chord tone.
Motive transformations
inversion = reverse interval directions · retrograde = reverse note order · augmentation = ×duration · diminution = ÷duration
A sequence moves the motive to a new pitch level; imitation restates it in another voice. Inversion, retrograde, augmentation, and diminution alter pitch direction, order, or rhythm.
Building a secondary dominant
V/x = major triad (or dom7) a perfect fifth above x’s root · V/V in C = D–F♯–A
The chromatic third of V/x is the leading tone of x and resolves up. A chordal seventh resolves down. Compare V/V (D–F♯–A) with diatonic ii (D–F–A): the F♯ is the tell.
Building a secondary leading-tone chord
vii°/x is built on the note a half step below x’s root · vii°7/V in C = F♯–A–C–E♭
Stack the chord in thirds from the target’s leading tone. A fully diminished vii°7/x = three stacked minor thirds; a half-diminished viiø7/x has a minor seventh on top and suits major targets.
Deriving a mode
mode on degree n = major scale starting from its nth note · D Dorian = C-major notes from D
Dorian = raised 6th · Phrygian = lowered 2nd · Lydian = raised 4th · Mixolydian = lowered 7th · Locrian = lowered 2nd and 5th.
Sectional forms at a glance
binary = A B · ternary = A B A (full return) · rounded binary = A B A′ (partial return within part 2)
Ternary’s A returns complete and independent after a contrasting B. Rounded binary tucks a shortened A′ into the end of the second reprise.
On the exam
- To name a sharp key fast, take the **last sharp and go up a half step** — that is the tonic (last sharp C♯ → tonic D). For flat keys, the **second-to-last flat is the tonic** (flats B♭ E♭ A♭ → tonic E♭). Memorizing these two tricks saves time on the exam.
- Watch the classic trap: **3/4 and 6/8 both contain six eighth notes**, but 3/4 groups them as three beats of two (simple triple) and 6/8 as two beats of three (compound duple). The grouping — not the raw count of eighths — determines the meter and the felt pulse.
- When you see a raised seventh degree used as an accidental in a minor-key passage, read it as **harmonic minor supplying a leading tone for the V chord**. That leading tone is what makes an authentic cadence possible in minor.
- Aural questions often ask you to hear texture. Train the cue: if a second melody enters that is as interesting as the first (a fugue subject, a round), it is **polyphony**; if the added parts merely fill in chords beneath the tune, it is **homophony**.
- Memorize the two ways the tritone appears: **augmented fourth (fa–ti, e.g. F–B)** and **diminished fifth (ti–fa, e.g. B–F)**. Spotting the tritone between scale degrees 4 and 7 is essential for identifying the dominant chord and voice-leading its resolution.
- Distinguish the two diminished sevenths by the top interval: **half-diminished (ø7)** has a **minor** seventh, **fully diminished (°7)** has a **diminished** seventh (a stack of three minor thirds). In major keys the viiø7 is common; the fully diminished °7 usually signals a minor key or a secondary function.
- On part-writing questions, resolve **tendency tones** without fail: the **leading tone (ti) rises to do**, and the **chordal seventh falls by step**. In a V7–I in C, B (ti) goes to C and F (the seventh) goes to E. Missing either resolution is an automatic deduction.
- In a parallel period, listen for the antecedent to end on a **half cadence (the question)** and the consequent to answer with a **PAC**. Identifying "HC then PAC" over two similar phrases is textbook evidence of a period — a frequent free-response and aural task.
- Recognize the **cadential 6/4** on sight: a tonic 6/4 landing on a strong beat before V, then resolving 6→5 and 4→3 over a held dominant bass (I6/4 → V → I). Many textbooks even label it V6/4–5/3 to show it is really an elaboration of the dominant, not an independent tonic.
- Remember the functional order **T–PD–D–T** runs one way. A dominant progressing back to a predominant (V → IV) is considered a **retrogression** and is generally avoided in common-practice writing — the exam expects predominants to lead into the dominant, not the reverse.
- When analyzing, first spell the underlying chord, then circle every melody note that is **not** in it. For each, mark the approach and departure. The classic 4–3 and 7–6 **suspensions** are frequent exam targets — look for a tie or repeated pitch that becomes dissonant and then falls a step.
- In fugue and imitative-texture questions, the **subject often reappears in augmentation, inversion, or both**. When you spot a familiar contour that is slower, upside down, or backward, name the specific transformation — that precise vocabulary is what earns the analysis point.
- To analyze any chromatic chord, ask: "**Does its chromatic tone lead into the root of the next chord by half step?**" If yes, it is very likely a secondary dominant of that next chord. Label it V/x (or V7/x), where x is the Roman numeral of the tonicized chord in the home key.
- When you find a **fully diminished seventh** in the middle of a phrase, test it as a **secondary leading-tone chord**: its root is a half step below the next chord’s root, and it resolves there. Because it is symmetrical, spelling (which note is the root) tells you which chord it tonicizes.
- Identify a mode by its **tonic and its one signature interval**, not by key signature alone — D Dorian and C major share the same notes but sound different because D is the tonic. Naming the characteristic degree (e.g. "Dorian: raised 6") is what secures the point on a modal analysis question.
- When labeling form, track **cadences and thematic return** together: cadences mark where phrases end, and the pattern of return (full = ternary, partial = rounded binary, none = simple binary) names the form. Diagram sections as A, B, A′ with their cadence types to justify your answer.
How to get a 5
- For melodic dictation, immediately identify the meter and the starting pitch relative to the tonic.
- Check your voice leading carefully: look specifically for parallel 5ths and octaves between every pair of voices.
- Remember to always resolve leading tones and the 7th of a dominant seventh chord (it resolves down).
- Sight-singing requires confidence. Sing loudly and keep going even if you make a mistake; rhythm is just as important as pitch.
- Spell before you judge. For any interval, chord, or scale question, write the letter names in order first and only then count semitones. Quality follows from letter names plus semitone count, so a candidate answer that changes the spelling — an augmented fourth versus a diminished fifth — is wrong even when it sounds identical.
- Practice the aural sections with a pencil moving. On melodic dictation, capture rhythm and contour on the first hearing, the starting pitch and cadence on the second, and fill in interior pitches after that. On harmonic dictation, notate the bass line first, then decide inversion from the bass–soprano interval, then assign Roman numerals.
- In part writing, work bass and soprano first as a correct two-voice framework, checking for parallel fifths and octaves between them, then fill the inner voices with the smoothest available motion. Most lost points come from the outer-voice pair, and fixing them later means rewriting everything.
- Sing or hum the leading tone and the chordal seventh in every progression you write. Those two pitches are where the graders look: the leading tone must never be doubled and normally rises to the tonic, and the seventh must fall by step. Getting only those two right recovers several rubric points.
- On the sight-singing task, spend the whole practice minute establishing the tonic and finding the hard leaps by relating them to the tonic triad. Sing at a slow, absolutely steady tempo — accurate pitch and continuous rhythm score far better than a fast performance that stops to correct itself.
Key terms
Major Scale Pattern — W-W-H-W-W-W-H (Whole, Whole, Half, Whole, Whole, Whole, Half)
Natural Minor Scale Pattern — W-H-W-W-H-W-W
Harmonic Minor — Natural minor scale with a raised 7th scale degree to create a leading tone.
Melodic Minor — Raised 6th and 7th scale degrees ascending; natural minor descending.
Diatonic Chords in Major — I, ii, iii, IV, V, vi, vii°
Diatonic Chords in Minor (Harmonic) — i, ii°, III+, iv, V, VI, vii°
Perfect Authentic Cadence (PAC) — V -> I (or i). Both chords in root position, soprano ends on tonic.
Plagal Cadence — IV -> I (or iv -> i). Often called the 'Amen' cadence.
Deceptive Cadence — V -> vi (or VI). The dominant resolves to a chord other than the tonic.
Half Cadence — A phrase ending on the dominant (V) chord, sounding incomplete.
Secondary Dominant — A major triad or dominant 7th chord that resolves to a diatonic chord other than the tonic (e.g., V/V).
Figured Bass Inversions (Triads) — Root: none (or 5/3). 1st inversion: 6 (or 6/3). 2nd inversion: 6/4.
Order of sharps and flats; finding the key — Sharps: F C G D A E B. Flats: B E A D G C F. Major key from sharps = a half step above the last sharp. Major key from flats = the next-to-last flat (one flat = F major). Relative minor = a minor third below the major tonic.
Interval qualities by semitone count — m2 = 1, M2 = 2, m3 = 3, M3 = 4, P4 = 5, A4/d5 = 6, P5 = 7, m6 = 8, M6 = 9, m7 = 10, M7 = 11, P8 = 12. Letter names fix the numeric size; semitones fix the quality.
Seventh chord qualities — Major 7 (M triad + M7), dominant 7 (M triad + m7), minor 7 (m triad + m7), half-diminished 7 (dim triad + m7, e.g., B–D–F–A), fully diminished 7 (dim triad + d7, e.g., B–D–F–A♭ — three stacked minor thirds).
Diatonic triad qualities — Major key: I, IV, V major; ii, iii, vi minor; vii° diminished. Natural minor: i, iv, v minor; III, VI, VII major; ii° diminished. Harmonic minor raises the 7th, making V major and vii° diminished.
Figured bass shorthand — No figure or 5/3 = root position. 6 (or 6/3) = first inversion. 6/4 = second inversion. 7 = root-position seventh. 6/5 = first inversion seventh. 4/3 = second inversion seventh. 4/2 (or 2) = third inversion seventh.
Cadence types — PAC: V–I, soprano on the tonic. IAC: V–I, soprano on the third or fifth. Half: ends on V. Plagal: IV–I. Deceptive: V–vi. Phrygian half: iv6–V in minor, bass falling a half step.
The seven modes on white keys — C Ionian, D Dorian, E Phrygian, F Lydian, G Mixolydian, A Aeolian, B Locrian. Dorian = minor with a raised 6th; Phrygian = minor with a lowered 2nd; Lydian = major with a raised 4th; Mixolydian = major with a lowered 7th.
Four voice-leading rules that cost the most points — 1) No parallel perfect fifths or octaves. 2) Never double the leading tone. 3) Resolve the chordal seventh down by step. 4) Keep adjacent upper voices within an octave and never let voices cross.
Non-chord tones — Passing (step in, step out, same direction). Neighbor (step away and back). Suspension (held over, resolves down by step). Retardation (held over, resolves up). Appoggiatura (leap in, step out, accented). Escape tone (step in, leap out). Anticipation (arrives early). Pedal point (sustained while harmony changes).
Secondary dominants and leading-tone chords — Build the chord on the leading tone or dominant of the target. In C major: V7/V = D–F♯–A–C; V7/ii = A–C♯–E–G; vii°7/V = F♯–A–C–E♭. Always spell the applied chord in the key of the target, then resolve to it.
Augmented sixth chords in a minor key — All place ♭6 in the bass and ♯4 above it. Italian: ♭6–1–♯4 (three notes). French: ♭6–1–2–♯4. German: ♭6–1–♭3–♯4. In C minor: It = A♭–C–F♯, Fr = A♭–C–D–F♯, Ger = A♭–C–E♭–F♯. The augmented sixth expands outward to an octave on the dominant.
Cadential six-four — A tonic-sounding chord over a dominant bass at a cadence: bass on the dominant with a sixth and fourth above, which resolve down to a fifth and third (V6/4–5/3). It is dominant in function, so label it V, not I.