Since Apple integrated Shazam into iOS 8 I'm using the app more and more. I hear a good song in my local coffeebar, longpress my iPhone's home button and a few seconds later it shows the title and artist of that song.
Shazam launched a Mac app today that does exactly the same thing. It runs as a menubar app that "continuously" listens to background noise. Once it finds the song it shows a notification on the Mac via Notification Center.
I said "continously" because luckily you can toggle it quickly on and off. I'd never want an app that listens to every sound and conversation that occurs around my Mac.
But for quick convenience, it's a great idea.
And yes, that's the awesome Bartender app keeping my menubar clean.