Music Theory Tutorial: Why Intervals?

In previous tutorials we learned about Notes that are the basic sounds in music. We then learned that it’s a good idea to group them into scales… the most important of which is the Major Scale. Finally we learned about the distances between notes called Intervals and how they are named relative to the Major Scale.

Having learned all that we’ve got a good foundation to take an advanced look at why you’d want to know your intervals well. We’ll take a whirlwind tour of music theory and show how knowing your intervals will help you learn and apply the theory and take you to the next level of musicianship.

Knowing the Major Scale

  • The major scale is the foundation of a lot of music theory
  • Knowing all the steps of each scale in all keys is very useful
  • Knowing the intervals is essentially knowing all the scale steps and the steps around them
  • Music moves at a very fast pace so having this information memorized and instantly available is very valuable

Building Chords

  • Chords are one of the fundamental building blocks of music
  • A chord is three or more notes played together
  • There are many chords so a system for defining and building them is necessary
  • Chords are often defined relative to the major scale
1 2 3 4 5 6 7 8
  • Above we see the C major scale with the scale steps numbered
  • Chords can be built using simple chord formulas naming the scale steps that are used
  • The table below gives some examples based on C Major
  • There are many chord formulas with many different sounds
Chord Steps Notes
Major 1 3 5 C E G
Minor 1 ♭3 5 C ♭E G
Diminished 1 ♭3 ♭5 C ♭E ♭G
Major 7 1 3 5 7 C E G B
Dominant 7 1 3 5 ♭7 C E G B♭
  • Needless to say knowing these scale steps in all keys lets you build chords easily and on the fly

Building Scales

  • Just as chords can be defined relative to the major scale so can other scales
  • Below are some examples
Scale Steps Notes
Major 1  2  3  4  5  6  7 C  D  E  F  G  A  B
Natural Minor 1  2 ♭3  4  5  ♭6  ♭7 C D E♭ F G A♭ B♭
Harmonic Minor 1  2  ♭3  4  5 ♭6  7 C D E♭ F G A♭ B
Hungarian Gypsy 1  2 ♭3  #4  5 ♭6  7 C D E♭ F# G A♭ B
Minor Pentatonic 1 ♭3  4  5 ♭7 C E♭ F G B♭
  • Needless to say knowing the scale steps/intervals of the major scale in all keys is invaluable to building these scales on the fly
  • There are more examples on this List of musical scales and modes (on Wikipedia). See the column labeled “degrees”


  • When improvising notes are played over a chord progression
  • Knowing what the “chord tones” are (the notes that the chord is built out of) is very useful
  • Playing the chord tones of the underlying chord often sounds “right”
  • Being able to immediately know what the chord tones are, which is a combination of knowing the scale tones/intervals and chord formulas, allows you to do that
  • The opposite is also true. If you play a note that sounds great you can use your knowledge of intervals to see how it relates to the chords you are playing over

Harmonizing the Major Scale

  • This topic will be covered very briefly. Full coverage is beyond the scope of this tutorial
  • Knowing which scale to use over a set of chords is important for composition/improvising
  • There are a certain set of chords that fit with a particular scale
  • You arrive at that set of chords by harmonizing the scale


  • To harmonize a scale you build chords for each scale step made only of scale tones in that scale. You start at each step and pick every second note from the scale
  • Above you can see the chords for each scale step of the C major scale. The major scale is circled in blue. The chords are build on each scale step
  • We learned that only the C major scale has no sharps or flats in it. So chords built from other keys may need to be adjusted so that they only use C major tones
  • The bottom line of the figure above has the names of the chords created
  • The chords for step 1, 4 and 5 have no adjustments so they are major
  • The other steps have chord tones that aren’t in their major scale so they are not major chords
  • For e.g. In order for the D chord above to be major it would have to have an F#. But since it has an F which is a ♭3 (minor third) instead it is a minor chord
  • The B diminished chord in addition to having a ♭3 has a ♭5 (diminished fifth) making it a diminished chord
  • This works for every key. By remembering the pattern (chord for step) above you can easily play the chords that go with any particular key
  • Knowing your intervals allows you to quickly find the root (bottom note) for the chord of each scale step in any key
  • Knowing your intervals lets you quickly understand why the chords for each scale step are the type they are (major, minor, diminished, etc)

Chord Progressions

I IImin IIImin IV V VImin VIIdim
  • In the last section we harmonized the major scale and noticed a pattern. For example the chord for step 1 (the one chord) is major, the chord for step 2 (the two chord) is minor, the chord for step 7 is diminished, etc
  • Above you can see this in a generic way. Each scale step is represented by a roman numeral and the chords that are not major have a “min” or “dim” next to them
  • We can use this pattern to describe chord progressions that can be easily transposed to many keys. Instead of saying a chord progression is: C G Amin F we could say that the progression is a: I V VImin IV progression in the key of C
  • If we know our intervals then we know the note at each scale position. We can then easily play the same progression in any key just by changing the the tonic (start note)
  • E.g. The I V VImin IV progression in B is: B F# G#min E


  • This has been a very brief whirlwind tour of the uses of intervals
  • We learned that chords are built using interval formulas (e.g.. 1 3 5) and knowing the intervals/scale steps of all major scales allows us to build chords easily
  • Scales are also built relative the the major scale
  • If you can easily determine the chord tones (by knowing your intervals) you can easily hit the chord tones while improvising
  • Harmonizing the major scale takes interval knowledge into overdrive to understand how it is done. If you know each scale step you can easily find the chord for each scale step
  • Using roman numerals to represent chords in a progression allows you to easily play progressions in any key
  • You can also do this in reverse by converting a series of chords to a generic progression which then can be transposed easily

Apps to assist you:

Having memorized the intervals in all keys opens the doors to a lot of theory and will take you to the next step in your understanding of music. A future tutorial will explain all the reasons intervals are useful. We have two apps specially designed to help you to learn the intervals:

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