What is "honk!"

HONK!, also known as HONK! Fest, is a festival of activist street bands held annually on Columbus Day weekend in Somerville, Massachusetts. Each year since 2006, an all-volunteer organizing community invites more than 25 bands from around New England, North America, and the world to participate in this free three-day event that showcases acoustic and ambulatory bands playing free music in public spaces. Since its inception, it has inspired additional HONK! festivals in other locations.