Chord Structure: Number System

The commonly-used convention for describing Chord Structure is a number system that uses the major scale as the point of reference…

The system works as follows:

• Numbers are assigned to each note in the major scale in ascending order.
• For example, in the key of C: C=1, D=2, E=3, F=4, G=5, A=6, B=7

• The number “1” always represents the root of the chord. Always!
• The other numbers correspond to notes in the major scale beginning on the root note.

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C Major Triad: Chord Structure = 1-3-5

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Chord Structures Larger than an Octave

In addition, chords that include “9ths”, “11ths”, and “13ths” are possible. Let’s add those to the mix in the key of C: D=9, F=11, and A=13…

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C Major 7, add 9: Chord Structure = 1-3-5-7-9

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Chord Structures Using Sharps & Flats

Chord tones are not limited to just the notes in a major scale. To include all possible notes, any of the numbers can be modified by sharps or flats.

Here are some examples…

C Minor 7th: Chord Structure = 1-b3-5-b7

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C Augmented Triad: Chord Structure = 1-3-#5

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Using the number system above, you can describe the structure of any chord type. Don’t worry about learning them all at this point. You will have lots more exposure to the naming conventions as needed in future lessons. For now, realize that knowing your major scales enables you to form chords with ease.

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learn more… Chords: Intervals