The backwaters and rivers of Kerala were the scene of vallam kali (vallam means boat and kali means play) since ancient times. They attain festive proportions during Onam season, the harvest festival of Kerala. Both men and women participate in the vallam kali. The different types of boats that participate in races are chundan vallam (snake boat), iruttu kuthi, churulan vallam, cheru vallam etc. Vanchipaattu is a kind of poetry, which is sung during vallam kali. These songs are rooted in nathonnatha vrutham, a pulsating rhythm, which resembles the crest and trough of the waves in the water. The rhythmic rowing of the oars by the rovers in the boats matches the rhythmic singing of vanchipaattu (song of the boat).
