This study focuses on the collection of twelve Sonatas by Lodovico Giustini (1685-1743), the earliest known pieces for the piano, which stood alone as such for at least thirty years. Giustini composed the collection for the hammered harpsichord, or fortepiano, invented by Bartolomeo Cristofori (1655?1731). This study also examines the connection between Giustini and the Brazilian priest João de Seixas da Fonseca Borges (1691-1758), sponsor of the Sonatas' publication in Florence (1732). Seixas dedicated them to Dom Antonio de Bragança (1694-1757), Infante of Portugal, a harpsichordist and pupil of Domenico Scarlatti (1685-1757). The research supplies biographies of the composer, the inventor of the instrument, the sponsor of the first edition, and the dedicatee of the collection. It also includes an overview on Cristofori's life in Florence under Ferdinando de Medici (1663-1713). Cristofori's achievements as the inventor of the forte-piano, or Arpicimbalo as he used to call his instrument will be also object of the study.