Weird music from my mac... please help!?

so for like over a year now my mac has just randomly started playing this weird pirate sounding music over and over... i quit everything and dont have limewire on my computer or widgets or anything like that and no one can seem to figure out what the hell it is.... UGH it makes me so frustrated haha because i have to shut down and restart my computer and even then sometimes it doesnt turn off... i wouldnt mind if it was like my music from my itunes that played or whatever but its literally the creepiest pirate music and it freaked me and my friend out one night we were just on facebook or whatever and we thought the computer was possessed hahaha... granted we werent in like the most "sober state" but it was scary and it continues to do it at random times......!! please help! thanks. xx.