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The Numbers  ♦  12   1  ♦  7 + 5  ♦   2   ♦  221-2221  ♦  EON for Triads  ♦  EON for 7ths

Guitar Chord Building - EON for Triads

chord building process from tones one through seven, each tone becomes root of chord and triads are built by taking everything tone from each root, eon is every other note

Once we are certain about the tones in the key of C Major, we build chords. Chords are created by selecting a root (a tone to build something from), and then selecting Every Other Note (EON). There are 7 tones in a Major scale; therefore, there are 7 triads (each tone becomes a root). Triads are 3 tone chords built by superimposing 3rds.

Note: We are using the terms note & tones interchangeably [EOT - Every Other Tone - not as memorable].

The C triad is made up of C-E-G, the D minor triad is made up of D-F-A, the E minor triad is made of E-G-B, & so on. Often, in chord scale playing, we substitute the V7 for the viio [the 3 tones of the diminished triad are the 3-5-7 of the V7].

We can use the math to see why chords are Major, minor, and diminished [dim or o]. Major triads have 4 half steps between the root and 3rd, & 3 half steps between 3rd and 5th. Minor triads have 3 half steps between the root and 3rd, & 4 half steps between 3rd and 5th [thus why we refer to the 3rd as a flat 3 in parallel thinking - it's one half step closer to the root]. Diminished triads have 3 half steps between the root and 3rd, & 3 half steps between 3rd and 5th [thus why we refer to the 3rd as a flat 3 & the 5th as a flat 5 in parallel thinking - both are one half step closer to the root].


  • Upper case Roman Numerals mean Major chords. Letters alone in the context of chords (not single tones) means Major [we don't have to write anything else].
  • Lower case Roman Numerals mean minor (yet minor is assumed for the 2, 3, & 6 chord, & you may see these sometimes written upper case). Little m next to a letter means that the chord is minor.
  • Lower case Roman Numerals with a superscript degree sign means diminished.


Once we create a Major scale by filtering out 5 tones using the phone number [221-2221], we can then use that set of 7 tones to create chords. The tones in the key of C are C-D-E-F-G-A-B-C [221-2221 applied to C as 1]. C is the only Major scale with only naturals (all of the sharps/flats are skipped).

These 7 tones make up the key of C. In music, a key is a group of tones that point our ear to one of the tones as home. It is the tonal center.

Every tone of a scale can become a root of a chord. Since there are 7 tones in the Major scale, we end up with 7 chords.

To build chords, we select a tone, then select every other note [EON], until we have 3 tones. Three tone chords built in 3rds (EON) are called triads. Triads have a Root, a 3rd, & a 5th. There are 4 types of triads [Major, minor, diminished, augmented. The tones & chords in a key could be called a family & we'll use this term occasionally.

The tones (scale) & chords that are a part of C are called diatonic to it. Diatonic means 'across the tones'. It means what is 'within the key' or 'a part of it'. Diatonic tones are inside.

In a Major key, the I, IV, & V are Major, the ii, iii, & vi are minor, & the viio is diminished. This is consistent in all Major keys.

The process we have applied to the key of C will be the same for all 12 tones. Since the tones are equally spaced [one-half step], & we are using the same filter [221-2221], & the same process for building chords [EON], the relationships are the same for every key.