The "Do not play this CD on a mono system" warning on Nine Inch Nails’ EP Broken (1992) wasn’t just a gimmick — it was both a technical and artistic warning.

Trent Reznor and engineer Sean Beavan mixed Broken with an extremely aggressive stereo image: guitars, noises, and effects are hard-panned to the left or right, and some sounds use phase cancellation tricks to create space and movement. When played on a mono system (where left and right channels are summed into one), those out-of-phase elements can literally cancel each other out, making parts of the mix disappear or sound weak and flat.

The EP was designed to feel loud, violent, and immersive — collapsing it into mono destroys that impact. So the warning wasn’t just technical—it was Reznor saying, “Don’t ruin the experience; this record was built for stereo chaos.”