Near the ancient site of Oc Eo, archaeologists have discovered an extraordinary set of avian bone whistles inlaid with tiny translucent quartz crystals. The whistles, which still produce high-pitched, bird-like notes, were found in a ritual pit located at the center of a prehistoric mound settlement, suggesting they were used for large-scale communal signaling or performance.
Contextual evidence, including the presence of frog-shaped clay figurines and water-lily impressions, leads researchers to conclude that these instruments were used in pre-Dong Son rain-calling ceremonies. These rites, held just before the monsoon season, appear to be the precursors to the elaborate water-themed festivals that define the cultural heritage of the Mekong region today.