Final answer:
The literary device being referred to is hyperbole, which is an intentional exaggeration used for rhetorical effect to create a strong impression.
Step-by-step explanation:
The literary device being described when a 'song' is referred to as an exaggeration for rhetorical effect is called hyperbole. Hyperbole is a figurative language technique where the speaker or writer intentionally uses extreme exaggeration to make a point or to create a strong impression. An example of hyperbole would be the line from William Wordsworth's poem where he describes a field of daffodils as 'ten thousand saw I at a glance,' which is not meant to be taken literally.