Christopher Marlowe's Doctor Faustus uses both blank verse and free verse to set the rhythm for the tale. Blank verse simply means that the lines do not rhyme; although it does follow iambic pentameter, making the lines melodious to read. Free verse refers to text with no rhyme or rhythm and results in a more whimsical sensibility.
Marlowe alternates the rhythm in the story depending upon whether he is establishing the main plot or referring to subplots. When he uses blank verse, the tone of the story is more serious and plot-driven. Free verse, conversely, is used during lighthearted—sometimes comic—moments. The use of the different writing styles can be seen as a cue to the audience as to whether or not the story should be taken seriously at any given time.