musical metaphor in Crowder

Tucked away in the liner notes  of the "A Collision" album, David Crowder writes of the song "Jerusalem, Our Happy Home":

 i believe that not only are we headed toward an eschatological encounter, but that God is as well in motion. toward us. momentum and consequence. there is a musical metaphor for this in the outro of this song. the acoustic guitar repeats the main riff of the song as the banjo plays the same melody in reverse. they drop one note on each sequential cycle through the melody until they dissolve into each other, finally concluding on the same note in the end.  link, complete notes