Music Theory Fundamentals

Essential theory concepts based on Rick Beato's teaching approach: intervals, chord construction, harmonic function, and voice leading.

Theory serves music: Music theory isn't rules to follow—it's a language to describe what already sounds good. Learn theory to understand why your favorite songs work, then use that knowledge to create your own music.

Intervals: The Building Blocks

What Are Intervals?

The distance between two notes

An interval is the musical distance between two pitches. All melody, harmony, and chord construction is built from intervals. Master intervals, and you understand the foundation of all music.

The 12 Chromatic Intervals (from any root note):

0 semitones = Unison (same note)

1 semitone = Minor 2nd (m2)

2 semitones = Major 2nd (M2)

3 semitones = Minor 3rd (m3)

4 semitones = Major 3rd (M3)

5 semitones = Perfect 4th (P4)

6 semitones = Tritone (♭5 or #4)

7 semitones = Perfect 5th (P5)

8 semitones = Minor 6th (m6)

9 semitones = Major 6th (M6)

10 semitones = Minor 7th (m7)

11 semitones = Major 7th (M7)

12 semitones = Octave (P8)

Intervals on Guitar

Visualizing intervals on the fretboard

Same string: Each fret = 1 semitone (minor 2nd)

Adjacent strings (same fret):

E to A, A to D, D to G = Perfect 4th (5 semitones)
G to B = Major 3rd (4 semitones)
B to E = Perfect 4th (5 semitones)

Octave shapes: Same note, 12 semitones higher

6th string → 4th string, same fret (e.g., E on 6th string, 0 fret = E on 4th string, 2nd fret)
5th string → 3rd string, same fret
Any string → 2 strings higher, 2 frets up

Interval Quality: The Character of Sound

Perfect intervals (Unison, 4th, 5th, Octave)

Stable, consonant, strong. Foundation of power chords and harmony.

Major intervals (2nd, 3rd, 6th, 7th)

Bright, happy, resolved. Define major tonality.

Minor intervals (2nd, 3rd, 6th, 7th)

Dark, sad, tense. Define minor tonality.

Tritone (♭5/#4)

Dissonant, unstable, demands resolution. The "devil's interval" that creates tension in dominant chords.

Chord Construction

Triads: Stacking Thirds

The foundation of all chords

Chords are built by stacking intervals of a 3rd (skipping every other note in a scale). A triad contains three notes: root, 3rd, and 5th.

Major Triad

Root + Major 3rd (4 semitones) + Perfect 5th (7 semitones)

Example: C major = C - E - G

Minor Triad

Root + Minor 3rd (3 semitones) + Perfect 5th (7 semitones)

Example: A minor = A - C - E

Diminished Triad

Root + Minor 3rd (3 semitones) + Diminished 5th (6 semitones)

Example: B diminished = B - D - F

Augmented Triad

Root + Major 3rd (4 semitones) + Augmented 5th (8 semitones)

Example: C augmented = C - E - G#

Seventh Chords: Adding Color

Four-note chords that define jazz, blues, and sophisticated harmony

Seventh chords add a 7th scale degree to triads, creating richer, more complex sounds. They're essential for jazz, blues, and modern pop.

Major 7th (Cmaj7)

Major triad + Major 7th (11 semitones)

C - E - G - B

Sound: Dreamy, jazzy, sophisticated

Dominant 7th (C7)

Major triad + Minor 7th (10 semitones)

C - E - G - B♭

Sound: Tense, wants to resolve, blues/rock staple

Minor 7th (Cm7)

Minor triad + Minor 7th (10 semitones)

C - E♭ - G - B♭

Sound: Smooth, mellow, jazzy

Minor 7♭5 (Half-Diminished, Cm7♭5)

Diminished triad + Minor 7th (10 semitones)

C - E♭ - G♭ - B♭

Sound: Dark, unstable, jazzy

Diminished 7th (Cdim7)

Diminished triad + Diminished 7th (9 semitones)

C - E♭ - G♭ - A (B♭♭)

Sound: Very tense, symmetrical, transitional

Extended Chords: 9ths, 11ths, 13ths

Continuing the pattern of stacked thirds

Beyond the 7th, you can continue stacking thirds to create 9th, 11th, and 13th chords. These are common in jazz and create lush, complex harmonies.

9th chord: 7th chord + 9th (2nd octave higher) = 5 notes

11th chord: 9th chord + 11th (4th octave higher) = 6 notes

13th chord: 11th chord + 13th (6th octave higher) = 7 notes

On guitar, we typically omit some notes (usually the 5th or 11th) because we only have 6 strings.

Diatonic Harmony

Harmonizing the Major Scale

Building chords from scale degrees

When you build triads on each degree of the major scale using only notes from that scale, you get a predictable pattern of chord qualities. This is the foundation of functional harmony.

Diatonic Triads in C Major:

I = C major (C - E - G)

ii = D minor (D - F - A)

iii = E minor (E - G - B)

IV = F major (F - A - C)

V = G major (G - B - D)

vi = A minor (A - C - E)

vii° = B diminished (B - D - F)

Pattern: Major - minor - minor - Major - Major - minor - diminished

This pattern is the same in every major key!

Diatonic 7th Chords

Diatonic 7th Chords in C Major:

Imaj7 = Cmaj7 (C - E - G - B)

ii7 = Dm7 (D - F - A - C)

iii7 = Em7 (E - G - B - D)

IVmaj7 = Fmaj7 (F - A - C - E)

V7 = G7 (G - B - D - F)

vi7 = Am7 (A - C - E - G)

vii°7 = Bm7♭5 (B - D - F - A)

Notice the V chord is a dominant 7th (G7), not Gmaj7. This creates tension that wants to resolve to I.

Functional Harmony

The Three Functions

How chords behave in a key

In tonal music, chords have functions—they create tension or release, movement or stability. Understanding function helps you write chord progressions that "make sense" and create emotional impact.

Tonic Function (Home/Stable)

Chords: I, iii, vi

Feel: Resolved, at rest, "home"

Songs often start and end on tonic chords

Dominant Function (Tension/Movement)

Chords: V, vii°

Feel: Unstable, wants to resolve to tonic

The V7 → I resolution is the strongest in music

Subdominant Function (Preparation/Away from home)

Chords: IV, ii

Feel: Moving away from tonic, preparing for dominant

Often leads to dominant chords

Common Chord Progressions

Functional harmony in action

I - IV - V - I (The most common progression)

Tonic → Subdominant → Dominant → Tonic

Examples: "Twist and Shout," "La Bamba," countless rock songs

I - V - vi - IV (The "pop" progression)

C - G - Am - F (in C major)

Examples: "Let It Be," "Don't Stop Believin'," "Someone Like You"

ii - V - I (Jazz standard)

Dm7 - G7 - Cmaj7 (in C major)

The backbone of jazz harmony

I - vi - IV - V (The "50s progression")

C - Am - F - G (in C major)

Examples: "Stand By Me," "Every Breath You Take"

Voice Leading

What is Voice Leading?

Voice leading is how individual notes (voices) move from one chord to the next. Good voice leading creates smooth, logical motion between chords. Bad voice leading sounds jumpy and disconnected.

Principle 1: Move each voice by the smallest possible distance (stepwise motion is smoother than leaps)

Principle 2: Keep common tones between chords (if C major and F major both have C, keep that C in the same voice)

Principle 3: Avoid parallel 5ths and octaves (classical rule, less important in modern music but still sounds better)

Voice Leading Example: I - IV - V - I

Poor voice leading (big leaps):

C major: C (root) - E (3rd) - G (5th)

F major: F (root) - A (3rd) - C (5th) ← E moved down to A (big leap)

G major: G (root) - B (3rd) - D (5th) ← A moved up to B, C moved up to D

Good voice leading (smooth motion):