Louis Renner Logo
Louis Renner GmbH

History of the Renner Piano Action

The mechanics for keyboard instruments

For our business friends and for all lovers of piano music, we give a brief overview of the history of the development of hammer action. However, it is only possible to point out milestones that brought about significant changes in the hammer mechanics models. As an introduction, a brief consideration should be given to the ancestors of the fortepiano.

At this point we would like to thank you for the historical mechanisms that were kindly provided by the Landesgewerbemuseum in Stuttgart. As a further source for our studies we used the excellent book "Masterpieces of Piano Making" by Franz Josef Hirt.

15th Century

The earliest information about a piano, which, strangely enough, must have been similar to a fortepiano, comes from a treatise written in Latin around 1440 by the Dutch artist Heinrich Arnold von Zwolle, which was only recently discovered in an archive of the Paris National Library. According to this one-off report, there was hardly any news about hammer-piano-like instruments until the end of the 17th century.

17th Century

In the age of the Renaissance and Baroque up to the end of the 17th century, key string instruments were known as the soft and sweet-wistful clavichord and the metallic-rustling keel piano, which was built as a spinet or harpsichord and is still known today and occasionally by this name is played. The timbre (sound spectrum) and the fullness of the tone resulted from the scaling and the way in which the strings are made to vibrate.

The Clavichord

With the clavichord, a metal pin or metal plate resembling a spatula is attached to each rear key. By pressing the key down, this pin is struck from below on horizontally lying strings, which run roughly parallel to the front of the key, which are thereby divided into a sounding length and made to vibrate. The metal pins are also called tangents. All tones produced in this way have a wonderful melt. A pleasant tremor can even be produced by pressing the button with alternating strength. The string sound only lasts as long as the strings are touched by the tangents. As soon as the key is released, the tones are muffled by the cloth drawn in on the mute side of the strings. The tone volume could also be moderately influenced by a differentiated attack. The mechanics were the simplest possible construction and had a very easy variety.

The Keel Piano

The spinet and harpsichord have a completely different type of string excitation. So-called docks (weak wooden plates), which are guided in rakes, rest on the keys backwards. In the upper part of each dock, a pointed quill - later a hard piece of leather - is attached to an articulated and resilient tongue. When a key is pressed, the docks between the strings are pushed upwards and the latter is torn by the protruding quill from below - like a sharp pluck - and made to sound.

When the button is released, the dock falls back due to its own weight, weighted down with lead, whereby the quill slides sideways past the strings by deflecting the tongue until the damper felt attached to the top end of the dock comes to rest on the strings and dampens them. The volume could only be varied slightly by this plucking. Other facilities were available for this.

The harpsichords were also built with multiple manuals, so that this instrument was able to assert itself through its full sound at larger concerts.

18th Century

In the 18th century the era of the fortepiano began, which today - developed to the most artistic and subtle perfection - serves as the ideal instrument for the house and podium.

The Fortepiano

With these instruments the strings are struck by hammers and with the oldest type also by tangents. So that the strings can sound, the hammers have to release the strings immediately after the strike. This meant that another mechanism had to be used. This is always done in such a way that the impact given to the hammers or tangents stops before they touch the strings.

In the simplest designs, only the key movement is limited by a bar, while in more developed designs the pusher leaves the hammer before it hits the stop and releases it completely so that it passes on the force it has been given to the strings and can fall back.

In the case of rebound tongue mechanisms, the hammers attached to the keys by means of a fork were driven off and triggered by the spatial movement of the hammer axes from the rebound bar or the rebound tongue. In order to slow down the relapse of the hammers, catchers were installed. Even later, further parts were added in order to hold the hammer in place or to lift it up again when the key fell back slightly so that the triggered impact element can be turned back into its impact position by means of a spring. This enabled a new stop to be achieved before the key returns to its rest position.

The repetition mechanism was invented through the appropriate attachment of such elements. Some of the earliest designs were also without damping devices.

In later, louder instruments, it inevitably had to be introduced everywhere. For the hammers, wooden cores were used that were originally bare or had leather furniture. Felts have also been used for around 100 years. Individual inventors also took other material.

The following should be mentioned about the development of the fortepiano: The mechanics of the first piano constructed by Heinrich Arnold von Zwolle around 1440 are described as tangent hammer mechanics, which are similar to keel piano mechanics - although not in essence, but in structure. Loose wood pusher (also called tangents), which are guided in rakes, rest backwards on the keys. Metal wires were attached to the head of these docks. According to the description, when a key was pressed, the lead-weighted tangents were thrown upwards, causing the horizontally lying strings to vibrate and immediately falling back onto the pressed key. The key depth was limited backwards by a bumper bar.

At the beginning of the 18th century, several inventors of new hammer mechanisms appeared before the public. Their ever-advancing inventions, some of which overlap, are extremely interesting. First of all, there is:


A Saxon named Pantaleon Hebenstreit, who caused a sensation with his concerts on a dulcimer, which was probably modeled after the Psaltery mentioned in the Bible and still found in the Orient. This dulcimer, which Louis XIV named "Pantalon" in honor of the inventor, was probably considered to be the forerunner of the fortepiano.

Around 1709

Bartolomeo Cristofori from Padua built a fortepiano with a new hammer action in Florence, and another construction by him from 1720 shows a mechanism with an astonishing degree of perfection for that time.

When the key is hit, the pusher, which is movably arranged backwards in the key, has actuated a driver, which translated the shock and passed it on to the hammer near the hammer's pivot point. Before this reached the strings, the jack was inevitably released so that the hammer could strike the strings and fall back, being slowed down by a catcher. After the button returned to its rest position, the pusher could slide under the driver cam again by means of a spring.

Behind the hammer there was a damping device in the form of a dock, the upper part of which, covered with fabric, sat on the strings. When it was hit, this damper was lifted off the keys so that the strings could vibrate freely. When the key returned to its rest position, the damper fell back onto the strings. For the hammers, among other things, strips of parchment rolled into rings were used, whereby the stop points of these rolls were garnished with leather. The rollers themselves were attached to wooden blocks that sat on a hammer handle. The triggering of the pusher could be regulated by a catcher-like cushion that was seated on a wire and served as a support.
Mechanics 1709 Bartolomeo Cristoori

Almost around the same time in 1716
Frenchman Jean Marius submitted designs of hammer mechanics to the Paris Academy, which he submitted independently.
Mechanics by Christoph Gottlieb Schröter 1717

Christoph Gottlieb Schröter, a German, proposed two new designs to the Elector of Saxony and King of Poland in Dresden, one with hammers hitting upwards and the other with hammers hitting downwards.

Around 1720

On the back of the button it had a flexible and springy push button that operated a driver. This passed the impact on to the vertically directed hammer by means of a movably attached intermediate pusher. To dampen the strings, articulated angle levers, which were attached to a bar above the hammers, were used and lifted off by a pusher on the key. It was probably the first overdamping with upright hammer mechanisms. From now on one differentiates the upright pianinos from the table-like grand pianos, a distinction that has remained to this day with mutual perfection.


Gottfried Silbermann built two pianos with bounce mechanisms in Freiberg near Dresden, where the hammer was articulated in a capsule on each key. When a key was pressed, the hammer was bounced against the strings due to the spatial movement of the hammer axes, in that the beak behind the axis was held in place by a baffle bar. According to Johann Sebastian Bach's information, Silbermann improved this mechanism even further, which has been known as the "German mechanism" for a long time.

Around 1740

Ten years earlier, individual instrument makers began to make their fortepiano in an upright position. These instruments were the ancestors of our pianos. Due to the vertical position of the strings, own mechanics had to be developed. Well known is an upright fortepiano by the Italian Domenico del Mela di Gagliano from these years, which had an articulated mechanism.
Joint mechanics installed around 1740.
Joint mechanics installed around 1740.

Even better known is the one in 1745

Mechanics built into his pyramid wing by Christian Ernst Friderici, a German from Gera. It stood behind the strings and was a modified version of the Cristofori model.

Around 1750

The "English mechanics" were brought to great renown around the middle of the century as the so-called push mechanics, the basic idea of ​​which goes back to Cristofori's invention of 1709. Around the same time Johann Matthäus Schmahl built harp-shaped table pianos with a spring pusher mechanism in Ulm The pushers, which were loosely seated backwards on the keys and guided in rakes, passed the push to the unleathered hammers. There was no actual triggering device. The push was limited by a baffle bar over the rear end of the key. A two-armed lever was used A well-preserved square piano equipped with this mechanism still exists.


Philipp Jacob Warth from Untertürkheim near Stuttgart built so-called "English mechanics" into his table pianos. He attached a jack on the back key, which was pushed back by a spring. Its movement was limited by two pins. This jack grabbed with hers leather-covered edge under a so-called hammer nose and passed on the shock.

The front-facing hammer was attached to a metal wire. With the pen behind the jack, it was adjusted so that it could trigger when a key was pressed and release the hammer.

After the button had returned to its rest position, the jack could again be under the hammer nose
slide. A damper was also provided.

19th Century

The century of the great pianists and composers dawned at the same time as the classical Empire style. Hector Berlioz started, followed by Chopin, Liszt, Clara Schumann, Wagner, d'Albert and others.

It is mainly thanks to them that the technique of the piano and the grand piano received a tremendous boost. After all, it was the artists who wanted to get the maximum performance out of the instruments and the instrument makers to ever greater progress
spurred on.


As early as the turn of the century, the construction of upright pianos, so-called pianinos, began in Vienna and the United States of America. In 1800 Matthias Müller, Vienna, had the Viennese reed mechanism with an upright hammer in his pianos


Soon after the turn of the century, William Southwell, Dublin, upgraded the upright hammer mechanics to include another, the sticker action trigger mechanism.


Its mechanical design was as follows: A joint was attached to the rear key, which was connected by an adjusting pin to a second joint located in the lifting link and passed the keystroke on to the jack, which was mounted in the lifting link so that it could rotate and resiliently. This shock was passed on to the hammer on a leather-covered roller fastened in the hammer handle.

Shortly before the hammer hit the strings, the angled butt tongue was released and could be precisely adjusted with the help of the manikin attached to the hammer beam. A second lever was resiliently attached to the lifting link and locked in place with a hook. This lever or so-called repeater shank was held in place at the appropriate time by a regulating screw located on the roller in the hammer handle, so that the hammer fell back onto this repeater shank and is carried by it when it was released slowly.

With a strong attack, the hammer pushes the repeating arm downwards, the former being braked by an adjustable catcher located in the slotted hammer handle. If the key is now left a little behind, the catcher releases the hammer, which is lifted up again by the repeating arm adjusted with the correct spring pressure, so that the jack can slide under the roller for a new stop before the key has returned to its rest position . This principle has been preserved to this day. The damping was actuated by the lifting link which was extended to the rear.
1825 grand piano mechanism by Sebastian Erhard


Around the middle of the 19th century, the famous virtuoso and piano maker in Paris, Henri Herz, simplified Erard's construction somewhat, giving it its almost final form. Fortepiano with these mechanisms were used by the most famous pianists at their concerts all over the world until the end of the century. Liszt, Clara Schumann, Rubinstein and many others, all were enthusiastic supporters of Erard's constructions. 

Then, as now, it was the artists who, through their virtuosity, placed ever greater demands on the instruments, strived for their perfection and thus fertilized piano and mechanical engineering. Again and again the piano makers and the mechanics workshops were encouraged to make small changes. Due to the increasing tone strength, heavier hammers had to be used, the rattling or knocking noises of the mechanics were almost completely eliminated, the axes and their bearings were continuously improved.


Robert Wornum the Younger, London, has made significant improvements to the piano mechanics, Uprigth Action, during these years. A jack was mounted on a rocker screwed onto the rear button, which could be precisely adjusted by means of an adjusting screw for precise and even triggering. With the help of the two screws in the rocker, any air in the air between the jack and the neck of the hammer could be removed.

The underdamping was actuated by an angle lever from the button. The hammer was caught on the front end of the hammer by a two-armed lever, which was also set in motion by the button by means of a pusher.
1845 piano mechanism by Robert Wornum


Around this time the piano mechanics got its shape, which is still valid today, through further arrangements to improve resonance. In this case, the jack was attached to a lifting link attached to the hammer beam. A catcher to slow down the released and falling hammer has also been relocated to the lifting link. A counter catcher attached to the front of the hammer nut was used for interception. In order to bring the hammer back to the rest position safely and quickly when the lifting link returns, the butt of the hammer had a ribbon that was hung in a ribbon wire attached to the lifting link. The piano mechanism by Johann Christian Schleip, Berlin, from the same period is similar to the mechanism by Robert Wornum, only the underdamping is lifted directly from the key.
1850 piano mechanism by Johann Christian Schleip
Around 1850 piano mechanism by Jean-Henri Pape

20th Century

Here, too, small changes are necessary again and again and are also necessary at longer intervals in order to be able to express new and changing musical styles.


Now the grand piano mechanisms have reached a degree of perfection that meets the highest demands and can hardly be surpassed. In response to the question: "What does the artist demand from a good mechanism today?", Dr. Walter Pfeiffer gives the answer in his "Key and Lever of the Piano". It reads: “The playing equipment of a piano is the more perfect, the less the player is aware of it and the longer it is able to retain its original expressiveness and delicacy, the easier it is to manufacture and install and the easier it is to adjust later on. 

These properties are the touchstone for the value of every single play mechanism; they are to a large extent a key to the historical understanding of piano mechanics. 'Unrestrained expressiveness' is by far the most important of them. To achieve it more and more generally and to assert it against growing demands is - now related to the whole piano - the most noble goal of our art. "This" unrestrained expressiveness "of a piano action leaves the whole volume range of an instrument from breathtaking pianissimo with a different touch can be heard until penetrating fortissimo. 

Yes, even more subtle, because depending on the attack, it must be possible to modulate the tone color. The performing artist today appreciates the variety of the instrument as well as the tonal quality. Some artist judgments show the varied view of the game type:
  • everyone agrees on the rapid repetition and nervousness in the variety.
  • the mechanism reacts to the lightest stroke.
  • The extremely pleasant way of playing, especially its rich nuance possibilities up to the extreme pianissimo, were not a frequent pleasure for me as a player as well as the ability to express themselves when playing thanks to the slightly appealing, excellent mechanics. It was not difficult for me to reproduce the works of Rameau, Schubert, Debussy and Ravel on such a beautiful grand piano.
  • the excellence of the playing was of benefit to Rameau, the beautiful richness of tone to Schubert, and these two qualities combined were perfect for the reproduction of the French masters.
  • the experience is always the same when you play your grand piano. He never let me down.
  • throughout the concert I felt a sense of security and complete engagement as a result of the magic that you have incorporated into the mechanics. its responsive mechanics allow the greatest delicacy of tone and all shades to achieve a truly effortless expression.
  • the playing is also extremely pleasant and, thanks to its very good weight balance, enables the most delicate shades as well as a pearly passage playing.  And modulation capability in all positions, with an almost ideal variety.
  • a famous piano maker writes to us:
  • “The variety of a grand piano is the product of cooperation between the mechanics factory, the keyboard factory and the piano maker. Perfect mechanics are the prerequisite for a good type of game. But she alone does not guarantee it. "
  • "We owe the improvement of the variety in the last hundred years mainly to the persistent demands and wishes of the concert pianists."

The Renner grand piano and upright piano mechanics

It is the result of the most mature construction in a manufacturing precision that can hardly be increased. In the details, the most diverse, often somewhat divergent wishes of our customers have been combined and united. Only selected, best material is used for our mechanics and is constantly monitored. During production, the tightest tolerances are used throughout in order to achieve the greatest possible uniformity, so that a fluid, precise variety with the most reliable repetition can be achieved with every mechanism. It is so well made that generations can enjoy it. If installed carefully, it meets the highest demands. It is the result of seventy-five years of experience. A customer gave us the opinion of a world-famous artist about the Renner mechanism: “The grand piano has to obey me, both in the piano and in its force and power. The Renner mechanism does this, and when it is perfectly regulated, the repetition is wonderful and the trills are only really expressed. recycle, so that there is a guarantee that only the best construction in connection with selected material is used in the Renner machine heads. Source: Festschrift for the 75th anniversary of the company in 1957
© 2021 Louis Renner GmbH