 The first two, the oval spinet (1690) and the spinettone, were probably intended for Ferdinando to play the continuo part in musical productions at Pratolino.The third instrument Cristofori invented for Ferdinando was the piano, which spread slowly at first (see "Fortepiano") but ultimately became one of the most important of all musical instruments.The invention of the piano is believed to have occurred in about 1700; Cristofori built several more pianos for Ferdinando during the remainder of the Prince's lifetime.