The Principle of String Transference. It's a beautiful thing I picked up from Ted Greene's Chord Chemistry. No other chord book is quite like it.
This is a simple method for tripling your chord form vocabulary. We guitar players call 'em 'grips'.
In the first bar of the diagram below, I've stated a very common grip for Cmaj7, with the root on the 5th string. Kind of overused, but it's a good candidate for illustrating the String Transference Principle. Notice how the notes of the chord are on string set 5-4-3-2.
In order to play this chord on string set 6-5-4-3, we move the entire shape verbatim so that the root is on the 6th string, 8th fret, as in the first chord of Bar 2. If you play the chord in this form you'll realize it's not the familiar Cmaj7 sound anymore.
This is where the Principle comes into play.
The Principle of String Transference states that when moving a voicing to a lower set of strings, any note that lands on the 3rd string needs to move 1 fret down. Looking at the second chord in Bar 2, we see that the F note needs to move one fret down to E, giving us a perfect Cmaj7 chord with the root on the 6th string.
But wait there's more.
In Bar 3, we revert back again to our original root on 5th string Cmaj7. This time we'll transfer this same chord shape to string set 4-3-2-1 as in the first chord of Bar 4. The root C is now on the 4th string, 10th fret.
The second rule of the Principle of String Transference states that when moving a voicing to a higher string set, any note that lands on the 2nd string needs to move 1 fret up. This is illustrated in the second chord of Bar 4, where the Bb on the 2nd string, 11th fret is raised to a B at the 12th fret.
The great thing about this Principle is that it also works with scales and arpeggios.
Play Hard and Prosper.