Navratri starts on Aso Sud Padvo. It lasts for 9 days which are meant for the worship of Shaktimaa (Parvati Devi). Tried of the harassment from Demon Mahishasoor, the Devtas requested Bhrahma, Vishnu and Shivji (Tridevs) to help them. Shaktimaa was born out of the anger of the Tridevs and fought with the demon for 9 days continuously. The demon was killed and therefore we celebrate these 9 days by singing Mataji's devotional songs with musical instruments.