Since their UMS debut in 1984, the Takács Quartet has performed in Ann Arbor more than two dozen times, and their nearly annual appearances are always a highlight of the Chamber Arts Series. This year, the cherished ensemble celebrates its 50th anniversary with a program that pairs Haydn and Beethoven, two innovators of the string quartet form, with Benjamin Britten’s rarely-performed String Quartet No. 2. Britten composed the quartet in 1945, and it premiered in 1945 on the 250th anniversary of the death of Henry Purcell, a composer he revered above all others. “Classical music doesn’t get much more life-enhancing than this.” (The Guardian, London)