Shazam is the best app that you can find out which is the song that plays now. Now it has become even more useful with its new automatic mode, which allows to listen to songs in the background.
This new feature comes with the latest update for the Android app and aims to make the whole process of detecting songs more efficient. You can turn the automatic mode when you go to a bar while traveling in the car while you are on the beach and the nearby restaurant etc.
This will help you in finding the songs, because you will not have to to open the app and to make it to find a song or melody. The update is available now. From several weeks, iOS version of Shazam has this automatic mode.