Intervals and root notes

An interval is the distance between two notes. Scales and chords are built by stacking particular intervals above a root, so knowing them first makes both easy to understand. You will count intervals in semitones and learn the guitar shapes for the most common ones.

By the end of this lesson you will be able to:

• Name the interval between two notes by counting semitones.
• Explain what a root note is and why the other notes are measured from it.
• Play a root, fifth and octave shape, and hear major and minor thirds.

An interval is the distance between two notes. The smallest practical unit is the semitone (one fret), and every interval is a number of semitones.

The root is the note you measure from. When you say "C major", C is the root, and the other notes of the scale or chord are described by their distance from C.

The common intervals above a root:

• 1 semitone: minor second (m2)
• 2: major second (M2)
• 3: minor third (m3)
• 4: major third (M3)
• 5: perfect fourth (P4)
• 6: tritone
• 7: perfect fifth (P5)
• 8: minor sixth (m6)
• 9: major sixth (M6)
• 10: minor seventh (m7)
• 11: major seventh (M7)
• 12: octave

The third decides whether a chord sounds major or minor. A major third is 4 semitones; a minor third is 3. Everything else in a basic triad is the fifth, a perfect 7.

On the guitar, an interval is just a fret distance on one string. Across strings, the shape depends on the strings involved, but one shape is worth knowing: root, fifth, octave. From a root on the 6th string, the fifth is one string up and two frets higher, and the octave is two strings up and two frets higher.

Hearing a major and a minor third.

1. Play A on the 6th string, fret 5. This is the root.
2. Play the note 3 frets higher (fret 8: C). Say "minor third". It sounds darker, a little sad.
3. Play the note 4 frets higher (fret 9: C♯). Say "major third". It sounds brighter.
4. Play the root, then the note 7 frets higher (fret 12: E). A perfect fifth sounds open and stable.

Now play the root, third and fifth one after the other: A, C♯, E is A major; A, C, E is A minor. You just heard the difference between major and minor in its smallest form.

Do these in order. Each one is small. Tick the ones you have practised.

• 1.Measure from the root

  4 min

  1. Play A on the 6th string, fret 5. This is your root.
  2. Play the note 3 frets higher on the same string (C). That is a minor third. Say its name.
  3. Play the note 4 frets higher (C♯): a major third. Listen to how it differs.
  4. Play the note 7 frets higher (E): a perfect fifth.

  You have it when

  • You can hear that the major third sounds brighter than the minor third.
  I practised this one

• 2.Root, fifth and octave shape

  4 min

  1. Play G (6th string, fret 3), then D (5th string, fret 5), then G again (4th string, fret 5). That is root, fifth, octave.
  2. Move the shape up to A (fret 5, then 7, then 7) and name each note.
  3. Try the shape at frets 7 (B) and 8 (C).

  You have it when

  • You can name the root, fifth and octave at four different positions.
  I practised this one

• 3.Hear the interval

  4 min

  1. Play a root, then a note 7 semitones above. Hum 'Twinkle, Twinkle, Little Star' to match it: that is a perfect fifth.
  2. Play a root, then a note 4 semitones above. Hum 'When the Saints Go Marching In': a major third.
  3. Play a root, then a note 3 semitones above. Hum 'Greensleeves': a minor third.

  You have it when

  • You can link each interval you played to its tune.
  I practised this one

No rush. Play each interval slowly, with a pause between the two notes, and listen to the sound of the gap. If you use a metronome, put it at 50 BPM with one note per click.

• Counting the starting note as one. Count the distance. From A to C is three semitones (A–A♯, A♯–B, B–C), not four.
• Confusing the interval name with the semitone count. Learn them as a pair: 3 semitones is a minor third; 4 is a major third; 7 is a perfect fifth.
• Treating the root as just 'the first note'. The root is the home note: everything else is described by how far it is from home.

Chords are made by stacking intervals. A major chord is a root, a major third and a perfect fifth. You will use that in the Module 3 lessons on chord construction; for now, you can already hear why major and minor sound different.

Short version (10 minutes)

Play root, minor third and major third from three different roots, listening to the difference.

Standard version (about 30 minutes)

Do all three exercises, then find a perfect fifth above each natural note on the 6th string using the shape.

• An interval is the distance between two notes, counted in semitones.
• The root is the home note that intervals are measured from.
• 3 = minor third, 4 = major third, 5 = fourth, 7 = fifth, 12 = octave.
• The root–fifth–octave shape moves anywhere on the neck.

You are ready to move on when you can honestly say:

• I can name the interval between two notes by counting semitones.
• I can play the root–fifth–octave shape at four positions.
• I can hear the difference between a major and minor third.