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, although 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. Leading cello virtuoso Maria Kliegel performs them here on a cello made by Stradivarius in 1693.