← Back to the Music Theory I outline The Course Maker
← Music Theory I outline
Week 9 · Lecture outline

Week 9 — Lecture Outline · Triads

Music Theory I · MUS 156 Fictional sample

Course: MUS 156 Music Theory I · Kenosis College
Instructor: Professor Hemsworth
Unit: Learning Unit 9 of 16 (Week 9) · two sessions per week
Objectives: SLO 4 (spell and identify triads in every quality and inversion) · SLO 7 (translate what you hear into names and notation — the spine)
Sessions: session 1 — teach · session 2 — studio + arpeggio sing-down

You already hear this. We're going to name what you already know.

Sung in Aural Skills I: arpeggios in all four triad qualities — and the do–mi–sol pattern the room has sung since unit 4 finally gets its chord name this morning. What is spelled here gets sung there as stacked sound.

Week at a Glance

The table below summarizes the unit in one screen.
The unit's big question "You've been singing a chord since week 4 without being told. What is it — and once three notes stack in thirds, what decides whether the stack sounds bright, dark, squeezed, or stretched?"
By the end of the unit, students can… (1) build a triad as root–third–fifth, stacked in thirds; (2) spell all four qualities — major, minor, diminished, augmented — on any root, from the interval recipes; (3) read and write the four triad chord symbols (C, Cm, Cdim, Caug); (4) harmonize any major scale with its diatonic triads and give the Roman numeral and quality for each degree; (5) name the diatonic triads of natural minor, plus harmonic minor's major V and diminished viio; (6) identify root position, first inversion, and second inversion by the bass note, and label them with the figures 6 and 6/4.
Key vocabulary triad, root, third, fifth, quality, major triad, minor triad, diminished triad, augmented triad, chord symbol, diatonic triad, Roman numeral, root position, first inversion, second inversion, figure, 6, 6/4, bass note
Materials Deck 9 · the Week 9 chapter · paper keyboards from Week 1 · root cards and quality-sort sheets (the second session) · a piano or keyboard in the room · students' own instruments welcome in the studio
Timing note 8 segments ≈ 150 min. Session 1 = Segments 1–6 (75). Session 2 = Segments 7–8 (75: studio 55 + sing-down 20). Scale to your own pacing.

Segment 1 — Ear first: the naming ceremony (8 min) · Session 1 opens

Hook (no notation on screen yet). Sing do–mi–sol with the room — the warm-up they've done every week since unit 4. Hold the three notes as three groups so all three ring at once. Then say it: "Congratulations. You've been singing a chord since week 4. It's called a major triad, and today you learn to spell every flavor it comes in."

  • This is the spine at its purest: the sound came first — weeks first — and the name arrives only now, after the ear already owns it. Say that out loud; it's the whole design of the course landing on schedule.
  • Where we stand: the midterm is behind them and Foundations is certified. Frame it exactly that way — "Nothing we do from here on re-tests whether you can read. You can. Now we take the notes you can name and start stacking them." Units 9–15 build chords, progressions, and charts out of certified vocabulary.
  • The promise (say it, then put it on the board): "By the end of this week you can hear four chord flavors and sort them, spell all four on any root, and tell the bass player which note of the chord to put on the bottom — by name."

Memory hook: "A chord is a spelled sound. You've had the sound for years; today you get the spelling."

Segment 2 — The stack: root, third, fifth (10 min)

Plain language first. A triad is three notes stacked in thirds — every other letter: C, skip D, E, skip F, G. The bottom of the stack (when it's packed in thirds) is the root — the note the chord is named after. The middle is the third; the top is the fifth — named for their interval distance above the root.

  • Line, line, line — or space, space, space. On the staff, a packed triad is a snowman: three noteheads on three adjacent lines or three adjacent spaces. That's the fastest visual check there is.
  • Every-other-letter is the law. C–E–G is a triad. C–D–G is not — D is a second above C, and the stack breaks. Letters first, exactly like intervals in units 6 and 7.
  • Interaction (2 min): call a root letter; the class answers with the two letters that complete its stack ("F!" → "A, C!" · "B!" → "D, F!" · "E!" → "G, B!"). Letters only, no accidentals yet — that's the next segment's job.

Misconception + cure:

  • ❌ "Any three notes played together make a triad."
    ✅ Cure: three notes make a sound; only three notes stacked in thirds make a triad. C–D–G is a real, usable sound (your guitarist calls something like it "sus") — but it isn't a triad, because no every-other-letter stack produces it. The word "triad" is a spelling claim, not a head-count.

Segment 3 — Four flavors on one root (14 min)

Ear first. Play C major, then C minor, at the piano — same root, one moved note. "Same chord?" The room hears the flavor flip instantly. Then play C diminished ("squeezed") and C augmented ("stretched"). Four flavors, one root — the ear sorts them before any spelling exists. Now name the machinery.

  • Quality is the flavor, and it comes from the interval recipe above the root — cite the two rulers from unit 6, now doing chord duty:
  • Major (M): M3 + P5 → C E G
  • Minor (m): m3 + P5 → C E♭ G
  • Diminished (d): m3 + d5 → C E♭ G♭
  • Augmented (A): M3 + A5 → C E G♯
  • The fifth is the frame, the third is the paint: major and minor share a perfect fifth and differ only in the third; diminished squeezes the frame (d5), augmented stretches it (A5).
METER: free    CLEF: treble
| <C4,E4,G4>/w | <C4,Eb4,G4>/w | <C4,Eb4,Gb4>/w | <C4,E4,G#4>/w |

Four whole-note chords on the treble staff, all rooted on C4: first C–E–G (major), then C–E♭–G (minor — the third lowered), then C–E♭–G♭ (diminished — third and fifth both lowered), then C–E–G♯ (augmented — the fifth raised). One root, four spelled flavors.

  • Chord symbols, the four this unit owns: C (a bare letter means major) · Cm · Cdim · Caug. Typed exactly that way in every quiz and AI session. Seventh symbols like Cmaj7 and the slash in C/E are unit 10's business — name that now so nobody front-runs it wrong.
  • Interaction — one-root drill (3 min): put G on the board; the class builds all four aloud from the recipes: G B D · G B♭ D · G B♭ D♭ · G B D♯. Spellings on the projector only after the room commits.

Misconception + cure:

  • ❌ "Quality just means mood — major is happy, minor is sad, and that's the whole story."
    ✅ Cure: the mood words are training wheels, and they wobble: plenty of aching songs sit on major triads, and minor grooves can be pure joy. Quality is an interval fact — which third, which fifth — that your ear registers as color. Learn the recipes and you can spell the color you're hearing, in any context, whatever the mood of the song.

Segment 4 — Harmonize the scale: one key, seven chords (14 min)

Plain language first. Take the C major scale and build a snowman on every step, using only the scale's own notes. Seven triads fall out — the diatonic triads — and their qualities land in a fixed pattern that is the same in every major key.

METER: 4/4    CLEF: treble
| <C4,E4,G4>/q <D4,F4,A4>/q <E4,G4,B4>/q <F4,A4,C5>/q | <G4,B4,D5>/q <A4,C5,E5>/q <B4,D5,F5>/q <C5,E5,G5>/q |

Eight quarter-note chords climbing the treble staff: a triad built on every note of the C major scale — C–E–G, D–F–A, E–G–B, F–A–C, G–B–D, A–C–E, B–D–F — and the octave C–E–G on top. Every note belongs to C major; only the qualities change as the stack climbs.

  • The quality ladder, same in all 15 major keys: M m m M M m d — say it as Roman numerals, where case carries the quality: I · ii · iii · IV · V · vi · vii° (upper case = major, lower = minor, lower with the little circle = diminished).
  • Have the room hear the ladder: play I, then ii, then vi — "which were major?" They'll know. Then play vii° (B–D–F) and let it squirm. That squirm has a name and a job, and unit 11 gives it both.
  • The naming payoff: do–mi–sol is ^1–^3–^5 of the major scale — the I chord. They've been singing the tonic triad since week 4.

Misconception + cure:

  • ❌ "Diminished means any chord that sounds dissonant or crunchy."
    ✅ Cure: diminished is one exact recipe — m3 + d5, nothing else. B–D–F is diminished because its intervals say so, not because it sounds tense. Plenty of tense-sounding stacks aren't diminished, and vii° played gently is barely a squirm. Spelling defines it; the mood word doesn't.

Segment 5 — Minor's grid (11 min)

Ear first. Play Wayfaring Stranger's opening chord territory — an A minor triad, low and dark. The room knows this world from unit 5. Now harmonize natural minor the same snowman way.

  • Natural minor's diatonic triads (a minor): i · ii° · III · iv · v · VI · VII — A–C–E, B–D–F, C–E–G, D–F–A, E–G–B, F–A–C, G–B–D. Qualities: m d M m m M M — the same seven chords as C major wearing different numbers, because relative keys share notes (unit 5 rent, paid again).
  • But listen to v. Play i → v → i in pure natural minor: E–G–B is minor, and the pull home is soft. Now raise the ^7 the way harmonic minor taught: V becomes E–G♯–B, major, and ^7 becomes vii° (G♯–B–D), diminished — and the lean toward home snaps into focus. Harmonic minor exists exactly to buy this dominant. (Its ^3 stack, the augmented III+ — C–E–G♯ in A minor — is where augmented triads live diatonically; touch it and move on.)
  • Interaction (2 min): class calls the quality ladder for natural minor from the board pattern, then names the two chords harmonic minor upgrades (v → V, VII → vii°).

Misconception + cure:

  • ❌ "Minor keys just recycle the major chart, so there's nothing new to learn."
    ✅ Cure: half true, and the half matters. Natural minor's grid is the relative major's chords renumbered — but real music in minor almost always raises ^7, which changes two chords (V major, vii° diminished). Miss that and every worship chart in a minor key will out-vote your spelling.

Segment 6 — Inversions, figures, and the AI-critique moment (18 min) · Session 1 closes (~75)

Ear first. Play C–E–G, then E–G–C, then G–C–E, slowly. "Did the chord change?" The room hears the same harmony with a different floor. Name it: the chord's identity comes from its root; which member sits lowest — the bass note — is a separate fact.

  • Root position: root in the bass (C–E–G). The packed snowman.
  • First inversion: third in the bass (E–G–C). Labeled with the figure 6.
  • Second inversion: fifth in the bass (G–C–E). Labeled with the figure 6/4.
  • The figures are shorthand from a 350-year-old accounting system — they count intervals above the bass, and we type them with a slash: 6/4, never 6-4 (a hyphen will mean something else entirely in unit 14). Root position technically carries 5/3, which is why nobody bothers writing it.
METER: 4/4    CLEF: treble
| <C4,E4,G4>/h <E4,G4,C5>/h | <G4,C5,E5>/h <C4,E4,G4>/h |

Four half-note chords on the treble staff: C major in root position (C4 on the bottom), then first inversion (E4 lowest — the figure 6), then second inversion (G4 lowest — the figure 6/4), then home to root position. One chord, three floors.

Misconception + cure #1:

  • ❌ "E–G–C is a different chord from C–E–G."
    ✅ Cure: re-stack it in thirds and the root announces itself: E–G–C packs into C–E–G, root C, so it's the C major triad whichever member is lowest. Inversion changes the bass, not the identity — same chord, different floor.

Misconception + cure #2:

  • ❌ "6/4 is a fraction — or some kind of time signature."
    ✅ Cure: figures count intervals above the bass note: a sixth and a fourth live above the bass of G–C–E. Nothing is divided, and the meter hasn't changed. If it helps: figures are to chords what apartment numbers are to buildings — labels, not math.

AI-critique moment (3 min, live on the projector). Paste into a chatbot: "Is E–G–C the same chord as C–E–G? One sentence." Read it aloud. Plenty of tools will call E–G–C a different chord, invent a name for it, or waffle. Have the room fix it: re-stack in thirds, find the root, C major triad, first inversion, figure 6. "All term the tool drafts and you judge — and your tutorial's audit this week runs on your own knowledge. Four flavors and two figures: you're equipped."

Why this makes you a better musician

This unit converts directly into Thursday-night currency. When the leader calls "Gm" mid-song, you now spell G–B♭–D in your head before the next downbeat instead of hunting frets and hoping. When the bridge suddenly darkens, you can say what happened — "the iv chord's back" — instead of "it got moody there," which means you can play into it on purpose. And the inversion vocabulary is a gift you hand your rhythm section: "put the third on the bottom" turns a mud-thick guitar-and-bass doubling into an arrangement — the bass walks to E while the keys hold C major, and suddenly the band sounds produced. The studio is exactly this: hear the flavor, sort it, spell it on any root, and voice it across the room like a band would.

Callback + tease + hand-off.

  • Callback: "Week 4 you sang do–mi–sol because we asked. This morning you spelled it in four flavors on any root. The ear was never behind — it was waiting for the vocabulary."
  • Tease: "Next unit — Seventh chords: stack one more third on top and the chords start talking — including the difference between the two 7s on every chart you've ever read."
  • Hand-off: read the chapter if you haven't; Tutorial 9 with your AI tutor is due before Week 9's second session — the studio's sort assumes its reps. Practice set, quiz, discussion, and the Spell the Call assignment close the end of Week 9.

Segment 7 — Studio: "Quality sort" (55 min) · Session 2

Run from the studio sheet (P-studio-week-09). Shape, for planning: ears-only sorting rounds (four bins: major, minor, diminished, augmented) → one-root spelling relays with root cards → who's-on-the-bottom inversion rounds with figures → voicing a triad across the room, one member per singer, then rotating the bass. The studio is the payoff enacted: hear the flavor, spell the call, hand the bass player the third. 20 points, graded in session; async make-up path (full credit) on the studio sheet.

Segment 8 — Arpeggio sing-down + quality lightning round (20 min) · Session 2 closes

The room sings arpeggios in all four qualities on solfège from one do — do–mi–sol for major, do–me–sol for minor (unit 5's syllables earning chord rent), then the squeezed and stretched flavors by ear against the piano. Then a 90-second lightning round: Professor Hemsworth plays a triad; the class calls the quality on the count of three; last rounds add "root position or not?" Close with the milestone said plainly: the room now spells what it has sung all term — and next week the stacks grow a fourth note. End-of-week items: practice set, quiz, discussion, assignment.

Instructor FAQ — common stumbles

The table below lists predictable Week 9 questions and quick cures.

Student says / does Quick cure
"Is C–D–G a triad? It's three notes." Three notes, yes; triad, no. A triad must stack in thirds — every other letter. No every-other-letter stack spells C–D–G. Real sound, different family.
Spells C diminished as C–E♭–F♯. Same piano key as G♭, wrong letter — the fifth of a C-rooted triad must be a G-something (C to G is a fifth by letters). d5 above C is G♭. Letters first, then quality: unit 6's rule, now load-bearing.
"Augmented and diminished sound the same to me — both weird." Play them side by side: diminished is squeezed (both upper notes pulled in), augmented is stretched (fifth pushed up). Weird ≠ interchangeable — and the recipes differ on both intervals. Sort by ear the second session; spell by recipe today.
Calls E–G–C "an E chord." Whose snowman is it? Re-stack in thirds: C–E–G. Root C, so it's C major with the third on the bottom — first inversion, figure 6. The bass note is a fact about the floor, not the name.
Writes the figure as 6-4. Slash, always: 6/4. The hyphen has a different job coming in unit 14, and this course never lets the two collide.
"In A minor, is the five chord E–G–B or E–G♯–B?" Both exist; pick on purpose. Pure natural minor gives minor v (E–G–B); the moment you want the pull home — which is most of the time — harmonic minor's raised ^7 gives major V (E–G♯–B) and diminished vii° (G♯–B–D). Unit 5 already taught the raise; this is why.
"Why does vii° get a circle but Cdim gets 'dim'?" Two dialects, one chord: Roman-numeral analysis marks diminished with °, chord charts write dim. Same recipe (m3 + d5). This course types Cdim in symbols and vii° in numerals — and reads both.
"Do I have to write 5/3 on root-position chords?" No — root position is the default and its figures go without saying. You only annotate the exceptions: 6 for first inversion, 6/4 for second.

Scope flag

This outline stays inside Week 9's thirteen ledger concepts (the triad as stacked thirds; the four qualities; diatonic triads in major and in minor including harmonic minor's V/vii°/III+; root position and both inversions; the figures 6 and 6/4; the four triad chord symbols) plus the naming of the long-sung do–mi–sol pattern, first assessed here by design. Seventh chords, their symbols, and slash-bass notation (C/E) are named only as next-unit destinations, never taught. The vii° "job" tease points at unit 11 without teaching function. All spellings cite the course theory reference.

~ Professor Hemsworth's edition · Kenosis College · built with thecoursemaker.com