When Vivaldi died in Vienna on 27 or 28 July 1741, his family had the task of disposing of the vast collection of manuscripts (mainly of his own works but also containing sacred music by other composers) he had left behind in Venice. By 1745 at the latest these manuscripts, bound into the twenty-seven volumes today belonging to the Foà and Giordano collections in the Biblioteca Nazionale of Turin, were in the ownership of a noble Venetian bibliophile, Jacopo Soranzo. Oddly, these volumes contain few sonatas of any description and none at all for one instrument and bass. Vivaldi must have retained autograph manuscripts of these works in order to produce neat copies in response to commissions, and one can only speculate about the reason for their absence. Perhaps they were sold off separately and subsequently perished. At any rate, their loss means that it is impossible to gauge with any accuracy how many cello sonatas Vivaldi produced during his long career as a composer, which began no later than 1705 (the date of his Op 1) and continued up to his death.