In the spring of 1825, Beethoven got terribly sick. Came close to dying, in fact. After his recovery, he revised a string quartet he'd been working on. He added a long, reflective middle movement — a musical "thank you" to God for his life. The Takacs Quartet plays Beethoven's "Heiliger Dankgesang" in the NPR studios. It's the third movement from Beethoven's Quartet No. 15, Op. 132.