3.1. Chordgram Positional Structure

The chordgram positional structure can be easily understood by defining a reference major scale, starting at the root of the chord to be notated. The seven degrees of the reference scale are then displayed as follows:

An easy way to remember this particular disposition of the scale degrees is to think of the root (1^st tone) as the “center”, the 2^nd and the 3^rd as “low”, the 4^th and the 5^th as “middle” and the 6^th and the 7^th as “high” scale tones, statements in obvious agreement with common usage.  

The locations of the seven digits are then interpreted as chord tone labels (see above), to be filled with relevant information about the chord tones themselves.

Extended chord tones (9^th , 11^th , 13^th) simply share the labels of their below-octave equivalents:

In the context of popular music, in which octave equivalence is more strongly assumed than in more formal styles, these positioning overlaps don’t lead to any relevant ambiguity.

One nice aspect of this representation is the clear-cut separation between the tetrad tones (3^rd, 5^th and 7^th) and the chord extensions (9^th, 11^th and 13^th), respectively stacked to the right and to the left of the root symbol. It works as a reminder of the very distinct roles these two sets of tones play in popular harmony, therefore making chord identification and analysis both easier and faster.

In a chordgram, the root label (‘1’ in the above figure) is filled with the conventional letter symbol for the chord root (including a sharp or flat, if needed). The remaining tone labels are filled with special symbols that act as modifiers, indicating the tones to be played and their individual departures from the reference major scale. The following sections give a complete description of the chordgram modifier set.