Thanks to Mike Barraclough who tipped me off about a curious app in the iTunes Store. It's called Retro-Fi and it transforms any audio source playing on your iPad into an AM radio station. So if you're listening to a podcast in the Safari browser or listening to music via iTunes or Spotify, activating the app puts the sound through a filter, adds a bit of fading, static and just a smattering of co-channel interference. The result sounds pretty authentic. You can adjust the levels of interference until it sounds just right. Why would you want this 99 cent app? Well I need it for a video I am making on the change from analogue to digital radio. It is brilliant! It's also pretty good at demonstrating to others what AM radio used to sound like - for those who no longer own a long-, medium- or shortwave radio. If you're a hi-fi enthusiast, you won't understand this app at all.