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Figure 2. Top view of a Steinway model M piano owned by the au- thor. From Giordano (2010) with permission from Oxford University Press.
ano," and (eventually) "piano." The motivation for the name was that the new instrument could play a note either softly or loudly, depending on the intent of the performer. The de- sire to be able to change the loudness from one note to the next was the prime motivation for the invention of the piano. Such control was not possible with the other main keyboard instruments of the day (the harpsichord and organ) and was quickly exploited by composers such as Mozart in the transi- tion from the baroque to the classical era. This capability was made possible by Cristofori's invention of the piano action.
The history of the piano action and how it was motivated by other non-keyboard instruments has been described in many discussions of the piano (e.g., Pollens, 1995; Good, 2002). In this article I focus on a different part of the piano story that has gotten less attention, namely, how the piano has evolved through various stages from the instrument of three hundred years ago to the modern piano that we have today. We see that this evolution was driven by a combina- tion of factors, including the demands of composers and musicians, advances in the available materials, and the prop- erties of the human auditory system. As acousticians, we know that a sound can convey information that is difficult to describe in words. For that reason, the online version of this article contains sound files with which you can listen to the
differences between early pianos and their modern counter- parts. The sound files along with a description of the instru- ments used in the different performances can be found at http://acousticstoday.org/the-invention-and-evolution-of- the-piano/.
General Design of a Piano
In order to appreciate how the piano has changed over time, it is useful to review the general design of the instrument. A schematic drawing showing the components of a single note is given in Figure 3. The player presses on a key that is one end of a lever that sets the action into motion. We have not attempted to show the action in any detail in Figure 3; it is a complicated system of levers and axles that transmits the motion of the key lever to the hammer (Giordano, 2010). In normal playing, the piano hammer is propelled toward the string at speeds of typically 1-4 m/s, corresponding to notes ranging from pianissimo to fortissimo. The hammer is re- leased from the action just before it collides with the string, traveling freely when it collides and then rebounds from the string. The use of a hammer to excite the string was what differentiated the piano from other keyboard instruments of the era, most notably the harpsichord.
Figure 3. Schematic (and simplified) design of the components that produce a single note. The vibrating length of the string extends from the nut to the bridge. The nut is often replaced by a different structure (the agraffe or capo tastro bar). From Giordano (2010) with permis- sion from Oxford University Press.
The design of the harpsichord is similar to that shown in Figure 3, except with the action and hammer replaced by a plucking mechanism. We won't consider that aspect of the harpsichord in any detail here, other than to note that the "amplitude" of the pluck was independent of how rapidly the harpsichord key was depressed (Good, 2002). Hence the player could not change the volume of a tone by pressing gently or forcefully. This was possible with the piano, due to the way the action propelled the hammer. Hence, Cris- tofori's invention of the action was crucial for the success of the piano and was the reason that it soon displaced the harpsichord as the most popular keyboard instrument.
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