The relationship between two notes played together is an interval.

From the diatonic scale of the root note

We measure the interval from the diatonic scale of the lowest note.

The lowest note is the root note.

Say D is the root note. Write the diatonic scale of D. The interval from D to F# is a major 3rd. The interval from D to A is a diatonic 5th. The interval from D to C# is a major 7th.

Why are the 3rd and 7th major?

What is the interval from D to Ab?

Common intervals

Common intervals are measured from the root to the major 7th.

Let us presume D is our root. Here are the common intervals of D.

  1. Root D
    Semitone D# / Eb
  2. Tone E
    Minor 3rd F natural
  3. Major 3rd F#
  4. Diatonic 4th G
    Flat 5th Ab (Devil's note, Tritone)
  5. Diatonic 5th A
    Augmented 5th A# (sharp 5th)
  6. Diatonic 6th B Diminished 7th Cb
    Dominant 7th C natural
  7. Major 7th C#
  8. Octave D

The Octave

From D to D through one instance of the diatonic scale is an octave.

The Flat 5th (Tritone)

The octave cuts in half at the flat 5th. The flat 5th is known as the devil's note and tritone. The devil's note is three tones from the root.

The diatonic 4th and 5th are either side of the tritone.

The Diatonic 4th

There is one kind of 4th, a diatonic 4th. The flat 5th is a semitone higher. The major 3rd is a semitone lower. When we talk of a 4th we talk of a diatonic 4th.

Major 3rd / Minor 3rd

Harmony is built in 3rds. The 3rd is major 3rd (from the diatonic scale) or minor 3rd (a semitone under the major 3rd).

Major 7th, Dominant 7th, Diminished 7th

There are three types of 7th. The major 7th is the 7th of the diatonic scale. The dominant 7th is a semitone lower than the major 7th. The diminished 7th is two semitones lower than the major 7th.

The diminished 7th is enharmonic to the diatonic 6th.

Diatonic 6th

The diatonic 6th is the only kind of 6th. A dominant 7th is a semitone higher. An augmented 5th is a semitone lower. When we talk of a 6th we talk of a diatonic 6th.

Test Yourself

Now you can name the common intervals between any two notes.

  • E to G is a minor 3rd (from the diatonic scale of E)
  • G to E is a diatonic 6th (from the diatonic scale of G)
  • C# to F is a major 3rd (F is enharmonic to E#)
  • G to Eb is augmented 5th (Eb is enharmonic to D#)
  • G to C is a diatonic 4th
  • G to D is a diatonic 5th
  • F to B natural is a tritone
  • B to F natural is a tritone

Can you see a pattern in the intervals and their inversions?

  Semitone Tone Minor 3rd Major 3rd Diatonic 4th Flat 5th / Tritone
inverted Major 7th Dominant 7th Diatonic 6th Augmented 5th Diatonic 5th Flat 5th / Tritone
  • A is the major 3rd of F. Well then, F is the augmented 5th of A.
  • B is the major 7th of C. Well then, C is a semitone from B.
  • C to F# is a tritone. F# to C is a tritone.

Music Theory

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