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

The Dorian mode is the second mode of the major scale and it's formula is: 1, 2, b3, 4, 5, 6, b7. When these notes are aligned in thirds (the heptatonic arpeggio), the numbers are as follows: 1, b3, 5, b7, 9, 11, 13. Knowing this information will help you organize your thirds based upon the prevailing harmony.