I just got to listen to a brand new CD today. It is called "Retrograss". The musicians are David Grisman, John Hartford, and Mike Seeger. The idea of the project was to put some of their favorite songs into the style af early, pre-bluegrass country music. Some of the comments in the booklet refer to dropping certain chords (i.e. in "Old Home Place" -key of G- there is a B chord and an A chord; the 3 and the 2 chord - they were dropped from the song. It is very much recognizable as the same tune, but the effect is very old-timey, and fun. Proving the point that just about any song can be worked down to only three chords.

Some of my favorite songs are those with only 2 chords. They let the natural rhythms of the music take over.