Mechanical organs can be all shapes and sizes. The smaller barrel organs are often heard on streets in Europe and is a common way of getting money from people who pass by. These types are sometimes called hurdy gurdies, but this is not true. Larger barrel organs can be found on fairgrounds and are loud so that they can be heard above all the other noise at a fair. Meanwhile, smaller barrel organs can be found indoors, and play songs when someone puts in a coin, similar to a slot machine. Some clocks have barrel organ mechanisms that play music at certain times, such as every hour.