The tension of the heavier strings demanded the strength of a metal frame. These thicker strings gave greater volume and brilliance to the piano. Introduced by Alphaeus Babcock in 1830, cross stringing allowed the strings to fan out over a larger section of the soundboard. This gave it more character and also relieved the crowding of the strings. As early as the sixteenth century, upright designs were already developed for the harpsichord, but it wasn't until the eighteenth century where many builders, especially in Germany, tired to apply the upright from to the piano-forte. It wasn't until about 1800 until the first satisfactory uprights were finally invented (Hamilton). .
When German builders tried to apply the traditional rectangular form of the clavichord to the piano-forte, the Square Grand Piano evolved. It was popular up until 1900 when the piano continually became more powerful and responsive. One of two outstanding improvements was from Sebastien Erard, who invented the double-repetition action in Paris in 1821. That invention allowed very rapid repetition. The second improvement was the full cast-iron frame, invented by Alphaeus Babcock in Boston in 1825. That invention was the basis for today's extended keyboard. Last but not least, the grand piano was developed. The grand piano of today incorporates the best qualities of early keyboard instruments. The cross stringing - a way to achieve greater richness of tone by passing more strings over the center of the soundboard- was invented by Alphaeus Babcock in 1830, but was not used in the grand piano until the second half of the nineteenth century (Grover).
On early fortepianos, the mechanism modernly known as the pedal was often manipulated by the knees. For example, you would raise a lever with your knee in order to lift the damper from the string. Pianos once had 5 pedals, and two of these pedals we still have today. The first pedal, which is the pedal on the right side, is the damper.