I really am not sure entirely if this has been documented or not, but after messing around and hitting the radio a bunch, it began to play the portal radio music. From then on, when placing the radio on top of building c, it played a new song (which seemed 'bugged') that i did not recognize. Furthermore, placing the radio near the hole in the Stalker room prompted the creepy HL2 song, and halfway through, a female combine(?) voice spoke a code, and sincei was unprepared, i was unable to have it written down or memorized. Further results pending. Taking the radio into the ARC Facility also coats it with blood when flashlight is off. Will try all other notable locations and update if warranted.