Guide to Chord Formation by Howard Wright (Howard@jmdl.com)
Chapter 2 : Intervals

2.0 : Intervals

This is a way of referring to notes by desribing the 'distances' between them.
G major scale: (Reproduced from chapter 1 for clarity. --SB)
Note of the scale    Distance up from root note    Actual note
------------------------------------------------------------------
  1  (root note)             0                        G
  2                          2 semitones              A
  3                          4 semitones              B
  4                          5 semitones              C
  5                          7 semitones              D
  6                          9 semitones              E
  7                          11 semitones             F#
  8                          12 semitones             G
In the G major scale above, we can see that the distance between the 1st note (or root note) and the 2nd note is 2 semitones - this is called a 2nd.

The distance between the root note (G) and the 3rd note in the scale is 4 semitones - this is called a 3rd.

Pretty easy so far.

All you need to do is count up from the root note using notes of the scale, and if you end up on the 5th note of the scale you have a 5th, if you're on the 7th note, you've got a 7th.

Surely it can't be that simple...?



2.1 : Interval Flavours

Well not quite. As well as major scales, there are minor scales. You could also have a 'weird' note or chromatic note that didn't fit into either scale. To cope with this, the intervals come in different flavours.

You can have a minor 3rd or a major 3rd.
You can have a normal 5th (perfect 5th) or an augmented 5th.
You can have a 9th or a flat 9th.

All that changes here is that the 'distance' or interval is either stretched or squeezed by one semitone (half step).

So a minor 3rd is a semitone less than a major 3rd.
An augmented 5th is a semitone more than a perfect 5th.
    You will see a few different terms here which mean the same thing.
  • An augmented or sharp interval means one semitone higher.
  • A diminished or flat interval means one semitone lower.
You also have minor and major intervals which differ by a semitone - the minor interval is one semitone lower than the major interval.

Here is a table of intervals with their corresponding 'distances' in semitones.



2.2 : Table of Intervals
Semitones    Interval
-----------------------
   0           Unison
   1           flat 2nd
   2           2nd
   3           minor 3rd
   4           major 3rd
   5           perfect 4th
   6           flat 5th (diminished 5th or augmented 4th)
   7           perfect 5th
   8           minor 6th (or sharp 5th/augmented 5th)
   9           major 6th
  10           minor 7th (flat 7th)
  11           major 7th
  12           octave
  13           flat 9th
  14           9th
  15           sharp 9th/minor 10th (just minor 3rd one octave higher)
  16           major 10th (just major 3rd one octave higher)
  17           11th
  18           augmented 11th
  19           perfect 12th (octave above perfect 5th)
  20           flat 13th
  21           13th
So to work out any particular note, say the major 6th of an A major scale, start with A, find the distance for a major 6th (9 semitones) and just count up from A.

You should end up with F#, so this is a major 6th up from A. (see chromatic scale - Appendix A).



So, to recap. Chords are described or 'spelled out' using intervals. These intervals tell you far above the root note the other notes of the chord are. By using the table above you can find out how many semitones you need to move up for any given interval.

Here is a simple example.
Bm7 - the spelling for this is: 1st, minor 3rd, 5th, minor 7th.
Start with B - count up 3 semitones for a minor 3rd - you get D.
Count up 7 semitones from B to get the 5th - F#.
Count up 10 semitones to get the minor 7th - A

So the notes are: B D F# A
So - if you know the spelling of a particular chord (i.e. the intervals which describe it) then it's simple to use the table above to find out what notes you need.

What if you don't know the chord spelling?

If you just have a chord name, like F#m9, then you need to know how this chord is built.

The basic building blocks of all chords are triads.


Guide to Chord Formation by Howard Wright
Reformatted and noded (with permission) by Space Butler
<   Introduction  |   Index   |   Triads   >

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