Watch the ii V I online guitar lesson by Brad Carlton from Guitar Lab: Caging ii V I
This lesson will cover the general theory of the ii V I progression. The major scale contains seven different notes and they are numbered from one through seven with eight being the octave. Roman numerals are used for the scale degrees and chords are built off each degree. The chords are built by using every other note of the scale. Triads are three note chords involving these notes. Because major scales always utilize the same intervallic construction records will always be the same according to what scale degree you are referencing. This means that I, IV, and V will always be major triads and ii, iii, and vi will always be minor triads. The seventh step, the scale produces a diminished triad. This means that in a ii V I progression we will always be dealing with a minor triad for the ii, and major triads for the V and I.
We will be organizing this progression in the key of D over the entire fingerboard in the following lessons.