By TYRAN GRILLO
The term “chamber music” can be quaint or constricting. In the first sense, it describes music played in a small space and on a smaller scale than, say, a symphony orchestra; in the second sense, a literal and figurative confinement that will never match the volume of said orchestra. Tuesday’s performance by cellist Steven Isserlis and fortepianist Robert Levin at Barnes Hall threw open the windows on both misconceptions. Throughout the evening’s all-Beethoven program, these established musical partners held conversation not only among themselves, but also with the immovable spirit of invention that was the composer’s gift. Beethoven was unprecedented in spotlighting the cello in such an intimate setting, and the duo’s traversal of the Cello Sonatas Nos.