AP Music Theory Unit 2 ReviewMinor Scales and Key Signatures, Melody, Timbre, and Texture

AP Music Theory Unit 2 takes the major-key foundation from Unit 1 and expands it into the full pitch toolkit you need for the rest of the course. You learn the three forms of the minor scale, relative and parallel key relationships, other scale types like chromatic and pentatonic, and how to name any interval by size and quality. The single biggest idea is the interval, because every chord, progression, and voice-leading rule later in the course is built from intervals. The unit also covers how music actually sounds, through melody, timbre, texture, and rhythmic devices.

What this unit covers

The three minor scales and how keys relate

• Natural minor follows the step pattern W-H-W-W-H-W-W. It is the "default" minor, the one the key signature gives you with no extra accidentals.
• Harmonic minor raises scale degree 7 by a half step to create a leading tone. That raise leaves an augmented 2nd between scale degrees 6 and 7, which is the scale's signature exotic sound.
• Melodic minor raises both 6 and 7 on the way up (to smooth out that augmented 2nd) and reverts to natural minor on the way down.
• Those raised 6ths and 7ths are written as accidentals in the music, never in the key signature. The key signature always reflects natural minor.
• Relative keys share a key signature but have different tonics. D major and B minor both carry two sharps. To find a relative minor, go down to scale degree 6 of the major key (or count down a minor 3rd).
• Parallel keys share a tonic but have different key signatures. D major (two sharps) and D minor (one flat) are parallel. A shift between them is called a change of mode.
• Closely related keys differ from the home key by no more than one accidental, and they are the most common destinations when a piece shifts keys. Distantly related keys differ by more.

Other scales: chromatic, whole-tone, and pentatonic

• The chromatic scale uses all twelve pitches, each a half step apart. Melodies that slither by half step are drawing on it.
• The whole-tone scale has six notes, each a whole step apart. With no half steps, it has no leading tone and sounds floaty and unanchored.
• Major pentatonic uses scale degrees 1, 2, 3, 5, and 6 of the major scale (five notes, no half steps). Minor pentatonic pulls five notes from the minor scale. Think folk tunes and the black keys of the piano.

Intervals: size, quality, inversion, and compounds

• An interval is the distance between two pitches, named by size (2nd, 5th, 7th) and quality (major, minor, perfect, diminished, augmented). A major 2nd and a diminished 7th are complete interval names; "a 7th" alone is not.
• Unisons, 4ths, 5ths, and octaves take perfect quality. 2nds, 3rds, 6ths, and 7ths take major or minor. Any interval can be diminished or augmented.
• Enharmonic equivalents sound identical but are spelled differently. An augmented 4th and a diminished 5th are both the tritone, but the spelling changes the name.
• To invert an interval, move the lower note up an octave. An interval plus its inversion equals a perfect octave, so sizes add to 9 (a 3rd inverts to a 6th). Quality flips predictably. Perfect stays perfect, major becomes minor and vice versa, diminished becomes augmented and vice versa.
• Compound intervals span more than an octave (a 10th is a 3rd plus an octave) and keep the quality of their simple version.

Melody, transposition, and transposing instruments

• Melody is pitch plus rhythm unfolding through time, often organized into motives (short reusable ideas) and phrases (musical sentences).
• Contour is the shape of a melody's rise and fall. Conjunct motion moves by step, disjunct motion moves by leap, and range measures the span from lowest to highest pitch.
• Melodic transposition moves a whole melody to a new pitch level while keeping every interval and rhythm intact. A C major tune moved up a whole step is the same tune in D major.
• Transposing instruments are instruments whose written notes differ from the notes that actually sound. A B-flat instrument like clarinet or trumpet sounds a major 2nd lower than written, so you convert written pitch to sounding pitch before analyzing a score. Instruments like double bass transpose by an octave.

Timbre, texture, and rhythmic devices

• Timbre is the distinctive color of a sound, shaped by how it is produced and by register (which part of an instrument's or voice's range is being used). You identify standard performance media by ear, such as string quartet, SATB choir, brass quintet, jazz trio, and solo piano.
• Texture describes how musical lines combine. Monophony is a single unaccompanied line. Homophony is melody with accompaniment or chords moving together. Polyphony is multiple independent melodic lines at once.
• Texture devices add detail to that description. Bass-line devices include Alberti bass (broken-chord pattern) and walking bass (steady stepwise quarter notes). Polyphonic devices include canon, imitation, and countermelody. Other useful labels are ostinato, doubling, solo/soli, tutti, and accompaniment.
• Rhythmic devices push against the meter. Syncopation accents weak beats or weak parts of the beat. Hemiola makes a passage feel like it has shifted between groupings of two and three. Cross-rhythm (polyrhythm) layers patterns that do not share a meter. Borrowed divisions swap in triplets (compound division in simple meter) or duplets (simple division in compound meter).

Unit 2, Minor Scales and Key Signatures, Melody, Timbre, and Texture at a glance

Why Unit 2, Minor Scales and Key Signatures, Melody, Timbre, and Texture matters in AP Music

This unit finishes the fundamentals layer of the course. Everything after it assumes you can spell minor keys instantly and name intervals without counting on your fingers, because chords are just stacked intervals and progressions are just chords moving between related keys.

• Interval fluency is the gateway skill. A triad is a stack of 3rds, a seventh chord adds another 3rd, and chord quality in Unit 3 is defined entirely by interval quality.
• Minor keys are not optional. Roughly half the analysis, dictation, and part-writing you will see can be in minor, where the raised leading tone from harmonic minor drives the harmony.
• Timbre and texture vocabulary is what lets you answer aural questions precisely. "Homophony with an Alberti bass" is an answer; "piano playing chords" is not.
• Transposing-instrument skills make full scores readable, which matters any time an excerpt includes clarinet, trumpet, or horn parts.

How this unit connects across the course

• Builds directly on major scales, key signatures, pitch notation, and meter from Music Fundamentals I (Unit 1). The circle of fifths you learned there now carries minor keys too.
• Intervals are the raw material for triads and seventh chords (Unit 3). If you can spell a major 3rd and a perfect 5th above any note, you can spell any triad.
• The leading tone created by harmonic minor powers dominant function, cadences, and voice leading (Units 4 and 5). Minor-key harmony depends on that raised 7th.
• Melodic features like motives, sequences, and contour return as embellishments and melodic devices (Unit 6), and key relationships set up secondary function and modulation to closely related keys (Unit 7). The non-major/minor scales preview the modes in Unit 8.

Key notation and chord types

• Minor key signatures: identical to the relative major's signature; find the relative major a minor 3rd up to notate them correctly in order on the staff.
• Accidentals for raised 6 and 7: harmonic and melodic minor alterations are written in the music as sharps or naturals, never built into the key signature.
• Interval labels (M, m, P, d, A): size number plus quality letter names any interval, such as M6, m3, P5, d7, A4.
• Tritone: the special name for the A4 or d5, the interval that splits the octave exactly in half.
• Inversion arithmetic: sizes add to 9 (2+7, 3+6, 4+5), perfect stays perfect, major and minor swap, diminished and augmented swap.
• Compound interval names: a 9th, 10th, or 11th is its simple interval plus an octave, keeping the same quality.
• Enharmonic spellings: same sound, different notation (D-sharp minor and E-flat minor; A4 versus d5). Spelling matters for analysis.
• Transposing instrument notation: a part labeled "in B-flat" sounds a major 2nd lower than written; "in F" sounds a perfect 5th lower. You apply the given level and direction to find sounding pitch.
• Texture shorthand on scores: solo/soli, tutti, ostinato repetition, and doubled lines all describe how the notation maps to the texture you hear.

Unit 2, Minor Scales and Key Signatures, Melody, Timbre, and Texture on the AP exam

This unit's content shows up everywhere because it is foundational. On the multiple-choice section, aural questions play an excerpt and ask you to identify the scale type, the mode (major or minor), the texture type or device, the performance medium or instrumental timbre, and rhythmic devices like syncopation or hemiola. Score-based questions ask you to label intervals, identify minor scale forms in notation, name key relationships, and determine the sounding pitch of a transposing instrument's written part.

On the free-response section, melodic dictation regularly uses minor keys, so you need to hear the raised leading tone and recognize melodic-minor motion by ear. Sight-singing also includes minor-mode melodies. Interval fluency is the hidden skill behind harmonic dictation and part writing, since wrong intervals mean wrong chords. One useful boundary to know is that aural questions will not ask you to name the specific letter name of a key; you identify mode and relationships, not "this is B minor," by ear.

Essential questions

• Why does one minor key signature produce three different scale forms, and what musical problem does each form solve?
• How do intervals function as the building blocks of every chord and harmonic progression?
• What makes two keys "related," and why do pieces tend to move to closely related keys?
• How do timbre and texture shape what a piece sounds like even when the notes stay the same?

Key terms to know

• Natural minor scale: the minor scale exactly as the key signature spells it, with the pattern W-H-W-W-H-W-W.
• Harmonic minor scale: natural minor with a raised 7th scale degree, creating a leading tone and an augmented 2nd between degrees 6 and 7.
• Melodic minor scale: minor with raised 6th and 7th ascending, reverting to natural minor descending.
• Relative keys: a major and minor key that share a key signature but have different tonics, like F major and D minor.
• Parallel keys: a major and minor key that share a tonic but have different key signatures, like G major and G minor.
• Closely related keys: keys whose signatures differ from the original by at most one accidental, the most common targets for key shifts.
• Interval quality: the modifier (major, minor, perfect, diminished, augmented) that pins down an interval's exact size in half steps.
• Enharmonic equivalent: two spellings of the same sound, such as an augmented 4th and a diminished 5th.
• Compound interval: an interval larger than an octave, named as its simple equivalent plus an octave (a major 10th is a major 3rd plus an octave).
• Melodic transposition: moving a melody to a new pitch level while keeping its intervals and rhythms unchanged.
• Transposing instrument: an instrument whose written pitch differs from its sounding pitch, such as B-flat clarinet or F horn.
• Contour: the shape of a melody's rise and fall, described as conjunct (stepwise) or disjunct (leapy).
• Alberti bass: a broken-chord accompaniment pattern in the bass, a classic homophonic texture device.
• Hemiola: a rhythmic device where the music temporarily regroups beats so a passage in three feels like two, or vice versa.

Common mix-ups

• Relative versus parallel keys. Relative keys share a key signature (C major and A minor). Parallel keys share a tonic (C major and C minor). If the tonic letter changed, you are dealing with relatives.
• The raised 7th in harmonic minor is not in the key signature. If you see consistent accidentals on scale degree 7 throughout a passage, that is your clue you are in minor, not that someone forgot a sharp.
• Interval inversion flips quality except for perfect intervals. A major 6th inverts to a minor 3rd, but a perfect 4th inverts to a perfect 5th. Diminished and augmented also swap.
• Homophony is not just "everyone playing chords." Melody with accompaniment counts as homophony too. Polyphony requires multiple lines that are each melodically independent, like a canon or countermelody.