Few works by Johann Sebastian Bach have given rise to more research and speculation than the 'Sei Solo', the sonatas and partitas for solo violin. From the search for models to dating based on stylistic features, from the identification of the paper used for the autograph from 1720 to the mysticism of numbers, no stone has been left unturned to solve the numerous riddles posed by this exorbitant work. The pieces in this collection are exorbitant in several respects. Not only does Bach go beyond what was customary at the time in terms of length, but the musical content and technical demands are also unprecedented, both in the context of contemporary violin music by other composers and within Bach's own oeuvre. As so often in Bach's oeuvre, an entire musical cosmos is explored in a single work.