Turning tone on its head can prove effective in creating more engaging stories, but difficult to achieve. One area to try this is character voice.
Consider the naïve narrator in Platoon. He's young, un-tested, unhardened in the opening. His soft voice sets up the audience to be wary, because we immediately see the juxtaposition of his tone/experience against the violent situation of the Viet Nam war. So we know he’s about to have a wake-up call.
Later he talks like a philosopher, lilting like a melancholy diary passage, as the screen shows men being gunned down. He's graduated to a spiritual voice, but viewers are still experiencing violence. This tells us he's numb.
Or consider Hannibal Lector, who was at times is romantic and whimsical about his descriptions of eating humans. Turning his POV tone on it's head and juxtapositioning it with context made him that much creepier.
So go play with your characters and see how you can turn their tone on its head and surprise your reader.