Using Shazam to pick up audio over internal soundcard / headphones

I recently discovered Shazam has an app for mac, it seems it works by listening on the built in mic (or any mic presumably).

I wondered if there was a way I could get it to listen to the soundcard instead? I typically listen to radio streams over VLC, through headphones and thought it would be awesome to be able to use Shazam for those unknown tunes.

I found out about the Audio MIDI Setup.app which you can create aggregate devices, I thought maybe I could somehow forward the output into the mic- but I don't really understand it exactly truth be told.

Is there a way I could get this to work?