Angalamman’s Amavasya tradition is not in tune with her fierce and forbidding form–she comes out instead and sits on a swing. One can go nearby and move her, as many take joy in doing. There is something gentle and loving about this marking. You don’t fear Her, though she often sits there with astras in her four hands. Thalaattu paattu or lullabies are sung to her. Her fierceness is soothed on this night. I guess after She frees Siva from the brahmahatya dosa (the sin of killing a Brahmin), her anger does not abate that easily–this understanding is so realistic, the anger needs to be specifically quelled and subsided. Because it persists, Amavasya is when she is ritually calmed and soothed. One can do this, on this night. It’s not a reception setting as we see at the end of a Brahmotsavam. Unjal utsavams for Devi are of a different character altogether.
Some of these traditions come from Melmalaiyanur, whose Angalamman is the most important in the region (and which site has a specific relation to this temple). Maybe also from Samayapuram, though that is a Mariamman temple (and our Mutthumariamman only marks Pournami, with a small puja for utsavar and ladies coming to read Lalita Sahasranamam).