Call it a spectrum of sound: When St. Ann’s Church gets buzzin’ and there’s a Ukrainian vocal outfit harmonizing onstage while a barrelhouse pianist pounds out the blues down the hall and a troupe of Native American dancers preps its updates of Mohawk and Hopi traditions in the wings, you quickly realize that scope is everything at the Brooklyn Folk Festival. This weekend’s gathering is the annual event’s ninth go-round, and the breadth of offerings continues to dazzle. Still-frisky vets, such as Jim Kweskin, Peter Stampfel, and John Cohen, mess with the music’s orthodoxies even as they genuflect to them. Celebrations of Clarence Ashley’s string magic, revivals of western swing, and jug band hijinks nudge historical notions into the present tense. And of course, a female accordion orchestra shares the bill with an “anti-consumerist gospel choir” and the politics of the Last Poets. In between there’s a workshop to help hone your protest-song skills, too. With 45 pissing all over our pluralism, you’ll need it.