Scientists were fascinated by the ghostly find: a human skeleton buried in an Aztec temple with a clay, skull-shaped whistle in each bony hand. But no one blew into the noisemakers for nearly 15 years. When someone finally did, the shrill, windy screech made the spine tingle. If death had a sound, this was it. Roberto Velazquez believes the Aztecs played this mournful wail from the so-called Whistles of Death before they were sacrificed to the gods. The 66-year-old mechanical engineer has devoted his career to recreating the sounds of his pre-Columbian ancestors, producing hundreds of replicas of whistles, flutes and wind instruments unearthed in Mexico's ruins. Among Velazquez's replicas are those that emit a strange cacophony so strong that their frequency nears the maximum range of human hearing. Chronicles by Spanish priests from the 1500s described the Aztec and Mayan sounds as sad and doleful, although these may have been only what was played in their presence. Velazquez meticulously researches each noisemaker before replicating it. He travels across Mexico to examine newly unearthed wind instruments, some dating back to 400 BC and shaped like animals or deities. He studies reliefs and scans 500-year-old Spanish chronicles.