I heard today that, during the age of arctic exploration, sailors sometimes reported hearing strange music. They’d be walking out on the pack ice, already a dangerous and lonely place, when the sound of church bells or gongs would appear out of nowhere. These songs could go on for hours. More than one sailor believed they were going insane.
Apparently, what they were hearing was the Pacific walrus (Odobenus rosmarus). They males can perform intricate songs and vocalizations for the females which can include a distinctive ringing noise. Almost exactly like bells. Who knew?
Update!: Watch as E.T. the walrus sings for the crowd! Courtesy of Point Defiance Zoo and Aquarium.
Sources: National Geographic Photography, anecdote