The main propulsion for harmonic movement in your chord progression will usually occur between the bass notes which are either a perfect 4th or perfect 5th apart. Here is a version of a I, IV, V again showing how the bass notes move in 4ths and 5ths.
When only power chords are used, the bass notes usually determine whether the song is either major or minor. In the above example, the sound would be minor.
Movement is also created when the bass notes move by an interval of a 2nd. The example below shows a progression which uses the chords form the G major scale which have roots that are a 2nd apart.
If you create a chord progression that is within a certain key, such as the example above, it's kind of difficult to make any sort of mistake.
In part 3, we will be looking over common tone substitution.