Think you've seen all there is to see in the deadly, paneled catacombs of Aperture Science? You might have missed this Portal 2 easter egg: A quartet of hidden-away, musically-oriented turrets, a video of which is posted after the jump. Or maybe you didn't miss it. We're not mind readers, you know.
Portal 2 is the sequel to 2007's Game of the Year and draws from the award-winning formula of innovative gameplay, story, and music that earned the original over 70 industry accolades. Features single and multiplayer co-op modes.