The middle pedal is the least understood of the three pedals found on most acoustic pianos of the modern era. The fact that its purpose is often misunderstood by many piano owners is, well, understandable. Unlike the right pedal, the middle pedal does not have a single, universal purpose on every piano. On a grand piano, your middle pedal could be a sostenuto pedal or a bass sustain pedal (lifting all the dampers in the bass section only). On a vertical piano, the middle pedal could operate a practice mute. (Note that a small minority of grand piano models offer a practice mute too, but it is operated by a hand lever under the keyboard, not the middle pedal) So, it’s no wonder that many piano owners, including professional pianists and teachers, are not entirely clear on what the middle pedal is supposed to do, or even how to use it. Luckily, we are entirely clear (we would be bad piano technicians if we weren’t), so allow us to explain.

The Original Sostenuto Pedal

Functioning sostenuto pedal prototypes were available as early as the 1840s, but it was not until the mechanism was standardized and patented by Steinway & Sons in the 1870s that the sostenuto pedal became a widespread feature of grand piano design. Because Steinway & Sons is an American piano maker, the sostenuto pedal first caught on with rival American piano makers. European and Asian piano makers were slower to embrace this feature, and some only began offering the sostenuto pedal in the late 20th Century.

The original purpose of the middle pedal, at least on mass-produced, factory-built pianos made after the mid-1800s, was to operate the sostenuto mechanism inside the piano. From the Italian word for “sustain”, the sostenuto pedal is a more selective and specialized type of sustain pedal than the right pedal (see The Right Pedal) and functions in a distinctly different way. While the right pedal lifts all of the dampers in the piano simultaneously as soon as you press it, the sostenuto pedal will do nothing if pressed by itself, leading some piano owners to believe that it’s broken. However, if your fingers are holding down one or more notes, causing the dampers for those notes to lift, then (and only then!) pressing the sostenuto pedal will catch those dampers that are already lifted and hold them up after the hands are removed from the keys. None of the other dampers in the piano will be affected. Since the sostenuto pedal allows only those notes that your fingers are depressing to continue sounding without any other notes on the piano being affected, it’s as if one had an invisible third hand holding down keys in one part of the keyboard, while the hands move away to play notes in other parts of the keyboard. The sostenuto pedal is meant to be operated by the left foot, so the right foot can operate the sustain (right) pedal as one normally would without losing the sound of the notes being held by the sostenuto pedal. Using the sostenuto pedal smoothly requires practice, and since there are few opportunities to use it in standard repertoire written before 1900, which covers A LOT of the repertoire most classical pianists play, many pianists have simply never needed to learn how to use it.

The Sostenuto Pedal in Vertical Pianos

Originally designed with the grand piano form in mind, it is challenging to design a working sostenuto mechanism for a vertical piano. A few high-end piano makers have created working versions of a sostenuto pedal for vertical pianos, but it is normally found only on the largest and most expensive vertical models offered by these manufacturers. In short, do not expect to find a middle pedal that offers a true grand piano sostenuto function on the vast majority of vertical pianos you encounter in your life. Even in the piano business in which we encounter more pianos per year than most people will encounter in their entire lives, we rarely see more than one vertical piano per year with a sostenuto pedal. True, most vertical pianos have a middle pedal, but chances are, it’s NOT a sostenuto pedal. (We will elaborate on the middle pedal in vertical pianos later in this essay)

The Bass Sustain Version of the Middle Pedal

Because the sostenuto pedal adds time and money to designing and building a piano and is used infrequently by relatively few piano owners, not all piano makers bother to add a true sostenuto mechanism to all, or even any of their models, even if a middle pedal is present. Therefore, some less expensive entry-level baby grand models and smaller inexpensive American-made vertical models offer a bass sustain pedal instead. A bass sustain is exactly what it sounds like: it sustains only the notes in the bass section of the piano. “Why only the bass?” you may ask. Firstly, is much simpler to build a mechanism that lifts whole groups of dampers at one time than a mechanism that selectively catches individual dampers in any register of the piano, the way a true sostenuto mechanism does. Secondly, the bass sustain is based on the principle that the way most music is written, the notes most likely in need of being held longer would be in the bass, a compositional device often referred to as a “pedal point”, a term borrowed from the bass pedals on a pipe organ. Bass notes ring much longer than the higher treble notes, so holding them longer as a separate group makes more sense than holding higher treble notes. The downside of a bass sustain pedal is that it cannot help you if the notes you want to hold individually are outside of the bass register of the piano. Also, because all of the bass dampers are lifted as a group, there will be some blurring of the sound as adjacent bass wires ring sympathetically with the played notes. Some pianists who have only known pianos with a bass sustain middle pedal have embraced it, but pianists who know how a true sostenuto pedal is supposed to work often take a disparaging view of the bass sustain version of the middle pedal.

The Practice Mute Version of the Middle Pedal

In most American-made vertical piano models built after the 1930s, especially the smaller spinet and console models, the middle pedal (if present at all) will be a bass sustain pedal. However, when Japanese-made pianos began selling outside of Japan in the 1960s, Western piano owners were introduced to the version of the middle pedal that had become the norm on Japanese-made vertical pianos: the practice mute pedal. It’s not that the practice mute did not exist before; there have been some large American-made vertical pianos from the early 1900s with factory-installed practice mutes. But with nearly ALL Japanese-made vertical pianos offering the practice mute as a standard feature on their largest and most capable models, many Americans raised in or after the 1960s with Japanese-made vertical pianos in their homes only know the middle pedal as a practice mute and are sometimes surprised to discover that the middle pedal has different functions on other pianos. Nowadays, the vast majority of vertical pianos made in Japan, Korea, China, and Indonesia offer practice mutes operated by the middle pedal as a standard feature, with many European manufacturers offering practice mutes on their vertical models as well. The practice mute middle pedal is still a rare feature on American-made vertical piano models, so if you are considering buying any number of American-made vertical pianos we offer in our inventory of used pianos, you will have to live without a practice mute.

Vertical pianos that offer a middle pedal practice mute have a thick strip of felt attached to a metal rail inside the piano that is suspended above the hammers that strike the wires. It is attached to the middle pedal via a series of rods, hinges, and springs. The pedal itself can be locked down by sliding the pedal to the left into a notch built into the piano’s cabinet so one’s feet can be free to operate the other two pedals. When the middle pedal is depressed, the strip of felt descends into the path of the hammers preventing them from hitting the wires directly. This reduces the volume of the piano dramatically, enabling the pianist to practice quietly enough that neighbors or housemates will hear little if any sound coming from the piano in adjacent rooms or apartments. Unlike the other pedals, which are designed to add expression to the music, and are meant to be applied continuously while playing, the practice mute is not designed to contribute anything musical to one’s playing. It is meant to be used only when it is necessary to practice quietly and to be left either on or off as needed.

Hopefully, with any confusion you had about the middle pedal now gone, you may now go forth into the world confident that you have sufficient knowledge to deal with any middle pedal configuration you find on any piano.

Until next time, thanks for reading.

Paul Yarish, RPT