Don't Let Your Deal Go Down is an old swing tune than was transferred to bluegrass by Flatt & Scruggs. Notice the chord progression is not the usual I, IV, and V pattern.
This arrangement of Don't Let Your Deal Go Down is a fantastic tool for learning how to play out of several different keys in the same scale. Practice tip: Play a lick over a specific chord, then try to replicate that lick in another key.
The advanced version of Don't Let Your Deal Go Down gives you an opportunity to practice developing your fluid lines between these interesting chords.