Changing one individual note in a monophonic tune absolutely can be horribly off key. Melody is harmony, and harmony is counterpoint; even with a single voice humming, if the tune is "classical" enough your brain understands intuitively where the chord changes are and what the bass line should be.

You don't need microtonal pitches to violently defy people's expectations.

(EDIT: Though you almost certainly do need microtonal pitches to precisely mimic the effects described in the text. But I think you certainly could do something horrible without them.)