I've got a book on the history of the company (that I got from a library book sale) but I haven't read it.
I don't think that they use subliminal messages in the recordings to get people to buy but there is psychological theory behind the recordings just as there is psychological theory behind painting a dining room's wall's green or the color selected for a waiting room.
Some "anxiety" in the music may be good for keeping shoppers moving (but that can become irritating when a shopper is stuck in a checkout line for over an hour).
Other recordings may be used to make the shoppers sentimental (open the wallet). Then again if one is sentimental for how things were (nostalgia) they may walk away empty handed/with regret seeing nothing but newfangled crap and at today's prices.
I'm listening to Christmas music when I can find one of my tapes or CDs because it just seems so inappropriate to listen to these recordings out of season.