All chords are basically structured exactly the same way
Chords are fundamentally Tetrads (4-note chords) constructed in the series of fifths, shown on the left, the back-bone of
the World of PITCH. For the direction of chord progressions, we will use the expressions "flattening" (for "descending") and
"sharpening" (for "ascending") because the flat notes are below and the sharp notes above.
Triads (3-note chords) are incomplete Tetrads.
Let's look at an example - see
THE USE OF COLOR
Construction of a chord
Two notes of every chord
(in this case, the root, "G", and the fifth, "D")
are already in the series of fifths:
they are the FRAME (primary notes) of the chord.
The third of the chord, major or minor, "B",
is placed inside the FRAME, almost in the center.
The seventh (or sixth)
is placed outside the FRAME, as close as possible to it:
the chord will possess a seventh, "F",
if it progresses "downward" a fifth in a flattening direction;
the chord will possess a sixth
if it progresses "upward" a fifth in a sharpening direction,
The third and seventh (or sixth)
are the secondary notes of the chord.
In musical compositions,
chords will not necessarily appear in the inversion presented.
It was chosen, however, as the most useful for explaining their structure.
In order to use general terms
that will apply to as many circumstances as possible,
the following terminology will be used.
The primary notes of the FRAME will be called:
the COMMON TONE (which is common to both chords of the progression)
the PROPER TONE (which is specific to each chord of the progression).
The secondary notes are:
the MEDIAN (the third, major or minor),
which determines the mode of the chord; and
the MOTRIX (the seventh or sixth) which imparts movement to the chord
and determines the direction which it will take.