Poorly shielded wires and speakers can pick up stations as well. My brother's cheap guitar amp would randomly pick up garbled bits of sound from radio stations (while not plugged into any power source)
SoundBlaster / Cambridge SoundWorks set of subwoofer and satellite speakers with long wires did this, too. Freaked me out when I suddenly heard voices inside my apartment at night. Turned out it had suddenly started to pick up a radio talk program.
