Background music may seem harmless, but it can have a powerful effect on those who hear it. Recorded background music first found its way into factories, shops and restaurants in the USA. Very soon it spread to other parts of the world. Now it is becoming difficult to go shopping or eat a meal without listening to background music. To begin with, background music was intended simply to create a soothing   atmosphere. Recently, however, it's becoming a big business. An American marketing expert has shown that music can boost  sales or increase factory production by as much as a third. But it has to be the light music. Lively music has no effect at all on sales. Slow music can increase receipts  by 34%. This is probably because shoppers slow down and have more opportunity to spot items they would like to buy. Yet, slow music isn't always the answer. The expert found that in restaurants slow music meant customers took longer to eat their meals, which reduced overall sales. So restaurant owners might be well advised to play faster music to keep the customers moving-unless, of course, the resulting indigestion  leads to complaints. An American marketing expert has found background music can   _  .
increase sales or factory production create a soothing atmosphere make people slow down make people forget their worries