Via the YouTube description:
Outdoor concert crowd cavorts at New York's Tompkins Square Park (East Village) on August 9, 1981 during the "Avenue B is the Place to B" concert. Bands performing at the park band shell (since torn down) that day included Pierce Turner, Essential Bop, Liquid Liquid, Science, and Certain General. The event was produced by Una Johnston and Phelan.
This video footage originally aired in late 1981 on the Manhattan Cable public access television show "New York Entertainment Scene"
Via the PreFab Int'l Videos Archive.