One of the great new features that Google packed inside Android 4.1 Jelly Bean was Sound Search, designed to recognize songs and to work similarly with Shazam and Soundhound.
However, the new application will not only provide users with info on the song that they are listening to, but it will also deliver a link to the Google Play Music Store, so that users could purchase it if they like it.
Although meant to work only on Jelly Bean devices, the app was ported to Ice Cream Sandwich handsets as well.
Initially released only with support for rooted devices, it can now be installed on unrooted smartphones too, and all those who own an Ice Cream Sandwich phone can take it for a spin.
More info on the matter can be found in this thread
on XDA Developers. The app installs a widget on your screen, which will deliver info on the song you are hearing when tapped.