See fortepiano. A dynamic mark (pf) directing the performer to attack the written note at the dynamic level of piano (soft) followed by an immediate increase in volume to forte (loud).Instrument invented by Bartolomeo Cristofor in the early 18th-century. It's name refers to its ability to grade volume-much greater than with the harpsichord. Keys control hammers that strike strings, making the pianoforte a keyboard instrument, a stringed instrument and a member of the percussion family. The grand piano has horizontal strings and the upright piano has vertical strings.