Key developments in piano design: Hammer Action, Iron Frame, Sostenuto Pedal

In the realm of musical instruments, the piano holds a special place. Its majestic sound and expressive capabilities have captivated audiences for centuries. However, behind this enchanting music lies a meticulous design and engineering world. This blog post will explore three key developments that have revolutionized piano design: hammer action, iron frame, and sostenuto pedal. These innovations have not only enhanced the capabilities of the piano but have also paved the way for new artistic possibilities.

Hammer Action: Revolutionizing Touch and Tone

At the heart of every piano lies the hammer action mechanism. This complex system of levers and hammers produces sound when a key is pressed. The hammer action directly influences the instrument’s touch sensitivity and tonal quality.

In the early days of keyboard instruments, such as the harpsichord, the keys were directly connected to the strings. This design limited the dynamic expression and nuances that could be achieved. However, with the advent of the piano, the hammer action mechanism was born, bringing a significant breakthrough to keyboard instruments.

The credit for the invention of the modern hammer action goes to Bartolomeo Cristofori, an Italian maker, in the early 18th century. Cristofori’s “escapement” mechanism allowed the hammer to return to its resting position after striking the string, enabling repeated notes and faster passages. This innovation greatly enhanced the touch and responsiveness of the instrument, allowing for a more nuanced and expressive playing experience.

Hammer action offers several advantages in terms of touch and tone. The mechanism allows pianists to control the force and speed of each key, providing them with precise control over dynamics and expression. Additionally, striking the strings with varying force and velocity enables a wide range of tonal colors, from delicate whispers to powerful fortissimos. This versatility allows musicians to fully interpret the nuances of musical composition and infuse their playing with emotion.

Today, numerous piano models incorporate advanced hammer action technology. Renowned manufacturers such as Steinway & Sons, Yamaha, and Bösendorfer have refined and improved this mechanism. Models like the Steinway Model D, Yamaha CFX, and Bösendorfer 280VC are highly regarded for their exceptional touch and tonal capabilities.

Iron Frame: Strengthening Structure and Sound

The structural integrity of a piano plays a vital role in its longevity and sound quality. As an instrument with immense string tension, it requires a robust framework to support the pressure exerted by the strings. The iron frame is a significant development that addressed this need.

In the early days of piano manufacturing, wooden frames supported the string tension. However, these frames were limited in their ability to withstand the pressure, resulting in instability and a restricted dynamic range. There was a clear need for improvement to create a more durable and sonically superior instrument.

The mid-19th century marked a turning point in piano construction with the Introduction of the iron frame. Piano makers such as Érard, Steinway & Sons, and Pleyel pioneered using cast iron or steel frames. This innovation provided the strength and stability to counterbalance the string tension, preventing warping and ensuring the instrument remained in tune for longer.

The iron frame revolutionized piano design by significantly improving stability and sound projection. Distributing the tension evenly across the piano’s structure eliminated the warping and collapsing issues. The enhanced structural integrity also allowed for a greater dynamic range, enabling pianists to play with more power and control. The iron frame’s contribution to sound projection was transformative, as it facilitated the development of larger instruments with longer strings, resulting in enhanced resonance and a richer, more vibrant sound.

The Introduction of the iron frame profoundly impacted piano design and construction. It became a standard feature in almost all modern pianos, serving as the backbone of the instrument. Manufacturers today prioritize using high-quality iron frames to ensure durability, reliability, and superior sound.

Sostenuto Pedal: Enhancing Expressive Possibilities

The Sostenuto pedal is a unique addition to the piano’s pedal system. Unlike the sustain pedal, which sustains all played notes, the sostenuto pedal selectively sustains specific notes while allowing others to decay naturally. This pedal adds a layer of control and nuance to the pianist’s expression.

The development of the pedal system in pianos evolved. Early keyboard instruments lacked pedals, but with the emergence of the piano, composers and musicians sought ways to enhance the instrument’s expressive capabilities. The pedals underwent various modifications and innovations, ultimately leading to the Introduction of the Sostenuto pedal.

The sostenuto pedal was invented in the mid-19th century by Jean-Louis Boisselot and Sébastien Érard. Its Introduction revolutionized piano performance by enabling pianists to sustain chosen notes selectively. This allowed for the complex layering of sounds and the creation of unique musical effects.

The Sostenuto pedal offers several advantages to both pianists and composers. By sustaining specific notes while allowing others to decay, pianists can create sustained harmonies, enhancing the richness and complexity of their performances. Composers, too, can explore new tonal possibilities by utilizing the sostenuto pedal to create distinctive textures and musical effects.

While not all pianos are equipped with a sostenuto pedal, it remains a sought-after feature in high-end instruments. Renowned piano manufacturers recognize the importance of this pedal in expanding the artistic possibilities for pianists. For example, Steinway & Sons offers models like the Steinway Model B and Model D with a sostenuto pedal, while Yamaha’s CFX concert grand piano also features this expressive addition.

Combined Impact: How These Developments Shaped Modern Pianos

The three key developments in piano design—hammer action, iron frame, and sostenuto pedal—have individually transformed the instrument. However, their combined impact has shaped the modern piano as we know it today. The interplay between these developments has created a symbiotic relationship, enhancing the instrument’s performance, touch, and expressive capabilities.

The hammer action, iron frame, and sostenuto pedal advancements have significantly improved piano design. Touch sensitivity, tonal versatility, stability, sound projection, and expressive possibilities have all been enhanced, allowing pianists to achieve greater artistic expression.

The improved design elements in modern pianos have also influenced the evolution of piano playing techniques. Pianists now have access to a broader dynamic range, enabling them to explore nuanced expressions and precise control over their performances. The enhanced touch sensitivity and tonal capabilities of hammer action, combined with the sustained harmonies made possible by the Sostenuto pedal, have opened up new avenues for musical interpretation.

These key developments have profoundly influenced music composition and performance styles. Composers have utilized the expanded capabilities of modern pianos to create intricate textures, dynamic contrasts, and innovative harmonic structures. Pianists, in turn, have embraced these advancements to bring out the nuances of these compositions and explore new realms of artistic expression.

Renowned pianists and composers throughout history have embraced these advancements in piano design. From Franz Liszt, who pushed the limits of expression with his virtuosic performances, to contemporary artists like Martha Argerich and Lang Lang, who captivate audiences with their masterful interpretations, these musicians have harnessed the capabilities of modern pianos to leave an indelible mark on the world of music.


In conclusion, implementing hammer action, iron frame, and sostenuto pedal has revolutionized the piano design and greatly enhanced the instrument’s capabilities. Hammer action has provided pianists with unparalleled touch sensitivity and tonal versatility. The iron frame has strengthened the piano’s structure, ensuring stability and improved sound projection.

The sostenuto pedal has expanded the expressive possibilities for pianists and composers. These developments have shaped the modern piano, enabling pianists to explore new artistic realms and captivate audiences with their performances. As the evolution of piano design continues, we can only imagine the future developments that will further enhance this magnificent instrument.