Aztec Death Whistles

Like Erik says: "Aztec Death Whistle is the name of my next band":

When odd, skull-shaped grave items were found by archaeologists decades ago at an Aztec temple in Mexico, they were assumed to be mere toys or ornaments, and were catalogued and stored in warehouses. However, years later, experts discovered they were creepy ‘death whistles’ that made piercing noises resembling a human scream, which the ancient Aztecs may have used during ceremonies, sacrifices, or during battles to strike fear into their enemies.