Bachus - As you mention, could use a little more documentation. You can change the instrumentation if you want. For example, change from an Acoustic Bass to a Slap Bass, etc. As for the chord progression, you can change chords while the Riff is playing and it will still follow you. Of course, the result varies on what and when you play any "extra" chords. We found it best to use along with other variations in that style as you suggest to change things up a little.