How is this possible?

There is music playing from my PC but NO messngers, media players or programs related to music is going on. This has started since I installed my router on sunday. Its annoying and I want it to stop. Is someone using my connection? I have a WPA on it. Im not an expert with routers so I installed it following a linksys representative. But anyways, yeah the music is annoying...it sounds like a live stream. My firewall didnt detect an intrusion or anything