In what way did the pianoforte improve upon the harpsichord?

The pianoforte marked a significant evolution in keyboard instruments largely due to its capability to allow for a greater variation in volume. This ability stemmed from its innovative use of hammers that struck the strings, as opposed to the plucking mechanism used in the harpsichord. As a result, musicians could play more quietly or loudly depending on their touch, giving them expressive control over dynamics for the first time in keyboard music.

This dynamic range opened new possibilities for composers and performers, enabling more nuanced interpretations of musical works. The instrument's sensitivity to touch meant that the emotional expressiveness of music could be conveyed more effectively, which was a major step forward in the evolution of keyboard instruments and ultimately contributed to the development of the Romantic musical style.

In contrast, the other options do not capture the primary advancements brought by the pianoforte over the harpsichord. The instrument is not necessarily lighter, nor does it have more strings, and its tone is not inherently sharper; the key improvement lies in the dynamic capabilities that enhance musical expression.