The second installment of Stefano Molardi’s survey of the complete organ works of J.S. Bach offers a program built around the mood and emotional impact of the featured works (either by similarity or contrast), centering around one of the greatest of the master’s cycles, the Dritter Clavierübung, a set of chorale preludes structured as an “organ mass”. Mr. Molardi selected two historical organs that Bach may have known, or at least of a kind he may have been familiar with, for these recordings.