Bach’s six unaccompanied Cello Suites, written around 1720 while he was in the service of the young prince Leopold of Anhalt-Cöthen, are the first truly virtuosic works written for the instrument. Each of the Suites consists of a series of dance forms; however, this simple description belies the astonishing variety and complexity of the music. Nearly three centuries after their composition, the Suites remain the supreme test of a cellist’s technical and musical capability. Prize-winning cellist Alexander Rudin plays a 1740 cello by Montagnana, and in the Sixth Suite, a contemporary five-string cello, the instrument for which this particular work was allegedly composed.