Lets say I'm some cable company where ninety percent of calls are people saying the cable is out even though you have a message up front saying so. When this person actually gets through they could have on-hold music that subliminally repeats "hey lard-ass, the cable will be back shortly why don't you go for a walk or ride a bike for a while?" Maybe the on-hold subliminals for a sales line would be something like "buy this product and you sure to be getting oral pleasure from your spouse or spousal life acquaintance".
Of course, the applications are endless. And they don't necessarily have to be devious, do they? How about a calm, reassuring "your mind is calm, your life is happiness" while on hold? Maybe not at a hospital or funeral home but you get the idea.