Kathryn Posin invites viewers into the world of a working artist in modern dance. It’s 1977 and Posin is choreographing a new piece for the Manhattan dance company she leads. As she starts rehearsals with the troupe, Posin also travels the country as an Affiliate Artist, sharing her joyful exuberance and sense of purpose in dance with local communities that might not otherwise have access to the performing arts. With humor and charm, Posin drills a high school physical education class and stages a small performance and Q&A on a tile floor in a Pittsburgh union hall. Posin’s talent is showcased in scenes from the first performance of her new work, a playful and dazzling dance set to Brandenberg’s Concerto No. 4 in G Major.