Naming and Building Intervals

Everything in music, from scales and chords to melodies and riffs, is built from intervals. Once you know intervals, chords stop being memorized shapes and become transparent structures. This is the highest-leverage module in the course.

The idea

An interval is the distance between two notes, measured in two ways at once:

• Number (2nd, 3rd, 4th and so on): count the letter names, including both ends. C to E is C, D, E, so it is a 3rd. Always.
• Quality (major, minor, perfect, augmented, diminished): the exact number of semitones.

The intervals inside one octave:

Semitones	Name	Short	From C
0	Perfect unison	P1	C–C
1	Minor 2nd	m2	C–D♭
2	Major 2nd	M2	C–D
3	Minor 3rd	m3	C–E♭
4	Major 3rd	M3	C–E
5	Perfect 4th	P4	C–F
6	Tritone (augmented 4th or diminished 5th)	TT	C–F♯ or C–G♭
7	Perfect 5th	P5	C–G
8	Minor 6th	m6	C–A♭
9	Major 6th	M6	C–A
10	Minor 7th	m7	C–B♭
11	Major 7th	M7	C–B
12	Perfect octave	P8	C–C

Pick a root and click through the intervals. Listen to each one played note after note and together.

Key facts:

• Unisons, 4ths, 5ths and octaves are perfect. They do not come in major and minor versions.
• 2nds, 3rds, 6ths and 7ths come in major and minor versions, one semitone apart.
• Make a major interval one semitone smaller and it becomes minor. Make a minor or perfect interval one semitone smaller and it becomes diminished. Make a major or perfect interval one semitone larger and it becomes augmented.
• Spelling matters. C–D♯ (augmented 2nd) and C–E♭ (minor 3rd) are the same two frets but mean different things. The letter count decides the number: C to D-something is always some kind of 2nd.
• Inversions add up to 9. Flip an interval upside down and a 3rd becomes a 6th, a 2nd becomes a 7th, a 4th becomes a 5th. Major becomes minor and perfect stays perfect. C up to E is a major 3rd, E up to C is a minor 6th.

On your instrument

Guitar: interval shapes are movable. Learn each interval as a small hand shape and it works everywhere on the neck. With the lower note on string 6 or 5, and “next string” meaning the next thinner one:

Interval	Shape	Example from 6:5 (A)
m3	next string, 2 frets lower	5:3 (C)
M3	next string, 1 fret lower	5:4 (C♯)
P4	next string, same fret	5:5 (D)
Tritone	next string, 1 fret higher	5:6 (E♭)
P5	next string, 2 frets higher	5:7 (E). This is the power chord.
m6	next string, 3 frets higher	5:8 (F)
M6	two strings over, 1 fret lower	4:4 (F♯)
m7	two strings over, same fret	4:5 (G)
M7	two strings over, 1 fret higher	4:6 (G♯)
Octave	two strings over, 2 frets higher	4:7 (A)

The B-string rule. Strings are tuned a 4th apart, except strings 3 and 2 (G to B), which are a major 3rd apart. Whenever a shape crosses from string 3 to string 2, move the higher note one fret up. The octave from 4:5 is 2:8, not 2:7.

Piano. Intervals are visual: count the keys, black and white. Use the keyboard to check what your ear tells you, and the guitar to build shape memory.

Ear anchors. Tie each interval to the opening of a tune you already know:

Interval	Going up	Going down
m2	“Jaws” theme	“Für Elise”
M2	“Frère Jacques”	“Mary Had a Little Lamb”
m3	“Smoke on the Water” riff, “Greensleeves”	“Hey Jude”
M3	“Oh When the Saints”	“Swing Low, Sweet Chariot”
P4	“Here Comes the Bride”, “Amazing Grace”	“Eine kleine Nachtmusik”
Tritone	“The Simpsons” theme, “Maria” (West Side Story)	“Black Sabbath” riff (second to third note)
P5	“Star Wars” main theme, “Twinkle Twinkle” (second to third note)	“The Flintstones” theme
m6	“The Entertainer” (third to fourth note)	Theme from “Love Story”
M6	“My Bonnie Lies Over the Ocean”	“Nobody Knows the Trouble I’ve Seen”
m7	“Star Trek” (original series) theme	“Watermelon Man”
M7	“Take On Me” (chorus, first two notes)	“I Love You” (Cole Porter)
Octave	“Somewhere Over the Rainbow”	“Willow Weep for Me”

If a tune here means nothing to you, replace it with one from your own listening. A personal anchor always works better.

Worked example

The “Smoke on the Water” riff, written as intervals above the first note G:

G|------3---5-------3---6-5-------3---5---3-----|
D|--5-------------5-------------5-----------5---|
    1   ♭3  4     1   ♭3  ♭5 4  1   ♭3  4   ♭3  1

Three things to notice. The riff uses only four notes: root, minor 3rd, perfect 4th and the tritone as a passing note. The first move, root to ♭3, is a minor 3rd: next string, 2 frets lower. And the famous “wrong” note is the tritone, which immediately falls a semitone to the 4th.

Exercises

1. Spelling drill (paper, 10 minutes a day for a week). Write every interval from m2 to M7 above these roots: C, G, D, A, E, B♭, E♭, F♯. Then write them below the same roots. Check yourself with the explorer above.
2. Shape drill (guitar, 5 minutes a day). Pick a random fret on string 6. Play the m3, M3, P4, P5, m7 and octave above it. Say the note names out loud. Then repeat starting from string 5, then from string 3 to feel the B-string rule.
3. Ear drill. Use the trainer in lesson 1.3. The goal for two weeks: 90% on ascending intervals, then descending, then harmonic.
4. Real-music hunt. Take three riffs or melodies you already play. Label the interval between every pair of neighboring notes.

Common mistakes

• Counting semitones only. “Three semitones” tells you the size, not the name. Count letters first, then semitones.
• Forgetting the B-string rule and wondering why a shape sounds wrong on the top strings.
• Learning intervals only upward. Riffs and melodies go down just as often. Practice both directions from day one.

Check yourself