Great classic example (no. 2) and a really interesting more modern take on the wedge concept in no. 1, Mike! You start off with the classic ominbus that prolongs V7 of D and extend it using the modern harmonies, but it still winds up resolving to D! Very nice!
If y'all are really interested in seeing (and hearing) how the great classical composers handled this idea, theodoregeisel gave a link to a whole list of examples on the web (http://www.musictheoryexamples.com/18VE.html
) where you can actually see and hear the music. What you'll find is that they often used just fragments of the omnibus, instead of the whole thing, or substituted diminished sevenths for one of the dominant seventh–type structures.
We've taken the voice exchange idea quite far in a short span of time. I think Mike's comments from 6/21/11 at 5:00 am should be reviewed. In a simple voice exchange pattern like the one he gives, the intervening harmony between the root position and first inversion chords is really inconsequential in the big picture, just a result of voice leading. When you turn that three-chord progression into a five-chord omnibus progression by filling in the space between the first and second and then second and third chords, the two resulting harmonies are still just the result of voice leading and are possibly even more inconsequential than the previous inconsequential chord.
Okay, this is all just analytical fun (really?). But what if one wanted to improvise over the set of harmonies contained in the three-chord voice exchange or the five-chord omnibus. Are the intervening chords still "inconsequential"? In the case of the three-chord voice exchange, the intervening chord is diatonic to the two surrounding chords (A7–Emin–A7), so I think you could ignore it and play, for example, A mixolydian for the whole thing. But as things get more chromatic, I think you'd have to consider the added non-diatonic notes and include them in your choice of chord scale.
I don't have as much experience improvising that many of you do, I'm sure, so please let me know what you think about this issue. My guess is that there are many ways to approach this.
This stuff is a whole lot more fun that yard work, which I've been doing all morning in 90+ degrees in Arizona. In think I'm going to play some guitar...