SAM MIDDLETON, “Jazz is Free As a Bird,” 1972 (mixed media oil and collage on board). | Courtesy GP Contemporary   LAST FALL, LEAFING THROUGH the catalog for the Oct. 6, 2016, African-American Fine Art sale at Swann Auction Galleries, an abstract painting by Sam Middleton (1927-2015) stood out. Titled “Jazz Is Free As A...