Audio marketing has existed since what seems like the beginning of time. Between playings of Fred Astaire and some other depression era musician – Grey Andrew and the Wallowers? – the wireless would bellow out a tinny recordings that implored listeners that they needed to buy John Liver’s World Famous Liver Salts as they cure what ails you; all during a crisp Sunday morning with Mr and Mrs Percy Smithers relaxing in their kitchen (Percy’s reading the paper and his wife is inexplicably still cleaning an endless pile of dirty dishes).