Watch the Playing Over The I Chord online guitar lesson by Brad Carlton from Guitar Lab: Thirds and Sixths

The Ionian mode is another name for the major scale, and the formula will be 1, 2, 3, 4, 5, 6, 7. When these notes are aligned in thirds (the heptatonic arpeggio), the numbers are as follows: 1, 3, 5, 7, 9, 11, 13. Knowing this information will help you organize your thirds based upon the prevailing harmony.