The_Complete_Idiot%27s_Guide_To_Music_Theory

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Part 5: Embellishing
A common chord progression that needs harmonized.
Simple block chord harmonies.
Isolating the top voice in the I-vi-IV-V chord progression.
Inverting the chords to vary the internal voicings.
Let’s consider the harmony you play as piano accompaniment. If you recall, we
used the following chord progression as an example back in Chapter 13:
As learned back in Chapter 13, a simple block chord piano accompaniment
(right hand only) to this chord progression looks something like this:
The triads you play as accompaniment represent three-voice harmony; you just
happen to play all three voices with one hand. All the chords are in the root
(noninverted) form of 1-3-5—which represents a problem. When you change
from chord to chord, all the harmony notes move in parallel to each other. In
terms of voice leading, this is often frowned upon.
It’s also boring.
You can prove this by isolating the top note of this chord accompaniment. Now
sing the succession of top notes as if you were singing backup vocals:
Like I said: pretty boring—and not particularly melodic, either.
A better approach is to vary the voicings of the chords so that the harmony
parts don’t have to move in parallel.
For example, you might keep the C chord in its normal root position, but
change the Am to the first inversion (C-E-A), the F to the second inversion
(C-F-A), and the G to the first inversion (B-D-G), like this: