by Gary Ewer, from “The Essential Secrets of Songwriting” website:
Songwriters are always looking for ways to be more creative with chords. Some of the best ways involve simple modifications, and chord inversions offer great bang for the buck.
You may know the term “inversion” by another term: “slash chords.” What it means is that a different note other than the letter name of the chord is played as the lowest-sounding note of the chord. This makes a subtle change to the sound of the chord, and can be an easy way to add to the palette of chord colours you might use in your song.
A C major chord uses three notes: C E G. If the chord symbol simply says C, that means that the C is the lowest-sounding note. If you would rather have E as your lowest-sounding note, place a slash (/) after the chord name, and the note E after the slash. So the chord symbol C/E means to play a C major chord with the note E on the bottom.
But the real question is: How do you use inversions like this to best effect?
In general, the good songwriter will use inversions to help make better sense of a jumpy bass line. By using inversions, you can smooth out that bassline. Here’s a good example:
C G Am Am7 Dm G C
By using inverted chords, you can create a smoother bassline that might be more desirable:
C G/B Am Am/G Dm/F G C
That’s not the only reason you might use inversions. The other main reason would be to avoid boredom in progressions that use one chord for a long time. By using inversions you can create arpeggios (“broken” chords) in the bassline where you might otherwise be sitting on one note.
Be careful in your use of inversions. An inversion has a way of making a chord feel a tiny bit unstable, and so you should not use too many inversions in a row without a root position chord.