Music theory Study Guide

📖 Core Concepts Pitch – Perceived highness/lowness of a tone; frequency (e.g., A₄ = 440 Hz). Interval – Distance between two pitches; the smallest is a unison; an octave = 2:1 frequency ratio. Scale & Mode – Ordered set of pitches within an octave. Western chromatic scale = 12 equal semitones; common scales: major, natural minor, harmonic minor, melodic minor, pentatonic, octatonic. Key Signature – Symbol set that tells which notes are consistently sharpened or flattened; defines the piece’s tonic and scale. Chord – Vertical stack of ≥3 pitch classes; quality = major, minor, augmented, diminished; triad = root‑third‑fifth. Harmony – How chords move (progressions) and relate to the tonal center; functions labeled with Roman numerals (I, ii, V, etc.). Rhythm & Meter – Rhythm = pattern of durations; Meter groups beats into measures (time signature tells beats per measure and beat unit). Texture – How many independent layers sound together: monophonic, homophonic, polyphonic; also density (thick vs thin). Form – Large‑scale layout (e.g., binary AB, ternary ABA, sonata‑allegro). Repetition vs. alteration creates unity and contrast. Dynamics & Articulation – Volume markings (p, f, mf…) and note‑shaping symbols (staccato, legato, tenuto, accent). --- 📌 Must Remember Octave ratio: $2:1$ (frequency doubles). Circle of Fifths – Order of keys moving up a perfect fifth (C–G–D…); helps with key signatures and modulation. Major scale formula: whole–whole–half–whole–whole–whole–half (W‑W‑H‑W‑W‑W‑H). Minor scale variations: Natural minor = Aeolian mode (W‑H‑W‑W‑H‑W‑W). Harmonic minor raises 7th (adds a half‑step leading tone). Melodic minor raises 6th & 7th ascending, lowers them descending. Triad construction: Major: root, major 3rd, perfect 5th. Minor: root, minor 3rd, perfect 5th. Diminished: root, minor 3rd, diminished 5th. Augmented: root, major 3rd, augmented 5th. Common chord progressions: I–IV–V–I (tonic‑subdominant‑dominant); ii–V–I (Jazz). Time signatures: top number = beats per measure; bottom = note value receiving one beat (4 = quarter note, 8 = eighth). Polyrhythm: simultaneous different meters (e.g., 3 : 2). --- 🔄 Key Processes Identifying Key from Key Signature Count sharps (F♯, C♯, G♯…) → key = a major key a perfect fifth above the last sharp (or use “order of sharps” mnemonic). Count flats (B♭, E♭, A♭…) → key = a major key a perfect fourth above the last flat. Building a Scale Choose tonic → apply whole/half step pattern (major or minor). Constructing a Triad Start with tonic → add notes a third and a fifth above (skip one scale degree each). Roman‑Numeral Analysis of a Progression Determine key → label each chord by its scale degree (I, ii, V, etc.). Voice‑Leading Check (Common‑Practice) Move each voice by the smallest possible interval; avoid parallel fifths/octaves; resolve leading tone up to tonic. Analyzing Form Identify repeated sections (A, B) → note any modifications (A′, B′). --- 🔍 Key Comparisons Major vs. Minor Triad – Root‑M3‑P5 vs. Root‑m3‑P5. Staccato vs. Tenuto – Short, detached note vs. full‑value note with slight emphasis. Monophonic vs. Polyphonic Texture – Single line only vs. multiple independent lines. Consonance vs. Dissonance – Stable intervals (P4, P5, octave, M3, m3, M6, m6) vs. unstable intervals (tritone, minor 2nd, major 7th). Harmonic Rhythm vs. Melodic Rhythm – Rate of chord changes vs. rate of note values in a melody. --- ⚠️ Common Misunderstandings “All fourths are consonant.” Only in certain contexts (e.g., pedal points); a perfect fourth above the bass can be treated as a dissonance needing resolution. “Octave equivalence means the same note.” Pitch class is the same, but octave placement matters for voice leading and texture. “A key signature fully determines mode.” It indicates the major/minor tonality; mode (e.g., Dorian) may share the same signature but differs in tonic and interval pattern. “Syncopation equals polyrhythm.” Syncopation shifts accents within a single meter; polyrhythm involves two simultaneous meters. --- 🧠 Mental Models / Intuition “Circle of Fifths as a Clock” – Imagine the circle as a clock; moving clockwise adds sharps, counter‑clockwise adds flats. “Stacked Thirds” – Visualize chords as building blocks: each new note is a third above the previous one. “Gravity of the Tonic” – Think of the tonic as a magnetic center; chords feel “pulled” back toward it, especially after tension (dominant). “Rhythm as a Grid” – Subdivide each beat into equal parts; syncopation = stressing the off‑grid positions. --- 🚩 Exceptions & Edge Cases Modal Interchange: Borrowing chords from the parallel minor/major (e.g., ♭VI in a major key). Neapolitan Chord: Flat‑II major in first inversion, often precedes V in minor keys. Altered Dominants: V7♭9, V7♯5 etc., used to intensify resolution to I. Micro‑tonal Scales: Quarter‑tone and neutral‑second intervals break the 12‑tone equal‑tempered assumptions. --- 📍 When to Use Which Choose Major vs. Minor Scale: Based on key signature (no accidentals → C major or A minor) and tonal center. Use Staccato vs. Tenuto: Staccato for lively, detached passages; Tenuto for expressive emphasis without shortening. Apply Roman Numerals vs. Nashville Numbers: Roman numerals for classical analysis (functional harmony); Nashville numbers for pop/lead‑sheet contexts. Select Form Labels (AB, ABA, Rondo): Identify repetition patterns; if a section returns twice separated by contrasting material, label as Rondo (ABACA). --- 👀 Patterns to Recognize “IV–V–I” in a major key → cadential progression. Ascending 5th sequence (e.g., Dm → G → C) → common in tonal music. Syncopated off‑beat accent often appears in 4/4 pop (e.g., accent on the “&” of 2). Triad inversion pattern: root position → first inversion (6) → second inversion (6/4) often signals a passing chord. Melodic minor ascent vs. descent – look for raised 6th/7th in the upward line. --- 🗂️ Exam Traps Choosing “major” for a chord with a raised 3rd but a lowered 5th – that’s actually an augmented triad. Identifying a “perfect fourth” as consonant in all contexts – in tonal harmony, a fourth above the bass is treated as a dissonance needing resolution. Confusing key signature accidentals with accidentals in the melody – a sharp in the key signature applies to every occurrence of that note unless canceled by a natural. Assuming “binary form” always means two equal-length sections – lengths can differ; the key change (e.g., A in tonic, B in dominant) defines the form, not equality. Reading “staccatissimo” as just “staccato” – staccatissimo is markedly shorter; mis‑reading can affect rhythmic accuracy. ---