I have no idea how it works but imagine this.
You listen to radio and hear some amazing track and you want to know what it is.. - you run this app while music plays!
You remember sounds of some song but cant find it... - you run this app and try to sing this!
Its not a new app but i am sure many people may not know it and its a life saver.
So download it for your phone and never ever ask people "Do you know what tune is playing?" just run it and get the artist and name right away.
For popular music it works 100% good and fast, with some drum n bass i had issues finding. Could been Dj mixes or less known tracks.