A nice idea with something of an obvious flaw – that's the HMV Listening Post app.Of course, the listening post was a staple of the record store before online streaming allowed us to sample music from the comfort of our own homes. So how does the new one work in the modern world? Well, it works via your iPhone.See a CD on the rack, take a picture of it and the technology in the app will find it and bring up preview clips from the tracklisting. If you like what you hear, a 'Buy CD' button will allow you to do just that – buy a hard copy of the CD.So useful, but you've probably already guessed the flaw. If you've taken a photo of a CD, there's a good chance that you are in a record shop. If you are, you probably want to buy it there rather than waiting for HMV to send it via Royal Mail. You can't even buy albums directly as a download or indeed, delivered to your PC. With CD sales declining, that's not exactly forward thinking.Saying that, you can do a search for albums without the photo, so you might want to order something when not in a record shop. Good idea, perhaps not quite there in the execution. But it's free and fun to play with if you're a music fan.