Backup in the style of Jim Mills. Check out how he uses a chromatic walk in both sections. That helps lead the listener's and the soloist's ear to the next chord. Also note how he begins the B section with pinches. This defines the chord change very well, and starting out with a different rhythm makes the change in the chord progression feel even more dramatic. Mr. Mills then follows up the pinches with rolls and Scruggs licks, the contrast seems to drive the rhythm of the tune even harder!