Watch the Pop: Technique 1 online guitar lesson by TrueFire from Rhythm Guitar Greatest Hits Vol. 1
In this example of a pop guitar style, I'm using my open A string as a pedal tone against all of the chords. The first six bars of music are the same three chords descending down the fretboard except I am inverting those chords every two bars. Those chords are A - E - D triads and they can be inverted three times.
Listen to how powerful using the pedal tone against the first three shapes sounds. A/A - E/A - D/A. Sounds great just doing that but when you couple this idea with the inverted chords, it just sounds amazing.
The bar chords at the end of the phrases are chord substitutions for the major triads we've been inverting in the first six bars. Let me explain the bar chords I'm playing are F#mi7 - C#mi7 - Bmi7. F#mi7 can also be seen as an A major triad with an F# bass note. C#mi7 can also be seen as E major with a C# bass note and Bmi7 can be seen as a D major triad with a B bass note. So, all I'm really doing is replacing the A pedal tone we were using over the 3 major triads with a different bass note on each chord. Now, the harmony and theory goes deeper than that and you should understand that each of those minor chords is the relative minor to the 3 major chords. F#minor is the "relative minor" to A major and so forth.
Another way of looking at this is to know that in the harmonized major scale of A major you have seven chords built from the 7 scale tones.
Those chords are; Ama(7) - Bmi(7) - C#mi(7) - Dma(7) - Ema(E7) - F#mi(7)- G#dim(mi7b5)
You can see at a glance that all of the chords we've played in our pop progression are in this harmonized scale, right? Good!
Here's the fun part, you can substitute certain chords for each other because they contain similar notes to each other as I mentioned before.
A major (I) can sub with F#mi (VI) & C#mi7 (III) - Dma(7) (IV) can sub with Bmi(7) (II) and Ema (E7) (V) can sub with C#mi (III) or G#mi7(b5) (VII).
I know this may be a bit bewildering but I thought I should share that with you. You can hear it works in a practical sense and if you take the time to study what I've just described you'll get it no problem.