Normally, when you play a piano key without holding the sustain pedal down, the sound stops as soon as you release the key. Pianists often get in the bad habit of using the sustain pedal as a crutch to cover mistakes or play with sloppy technique. Owing to the desire of composers and players to imitate the sounds of the Turkish military marching bands, piano builders began including pedals on their pianos by which snare and bass drums, bells, cymbals, or the triangle could be played by the touch of a pedal while simultaneously playing the keyboard. Sostenuto in Italian means sustained.  "[This pedal] introduced a kind of reverberation effect to give the instrument a fuller, richer sound. An example of this is in measure 15 of “Claire de Lune” by Claude Debussy. To understand what it does, it’s worth considering the mechanics of how an acoustic piano works. The Blüthner aliquot system uses an additional (hence fourth) string in each note of the top three piano octaves. Make sure to grab the sheet music for your favorite piano pieces at Musicnotes.com, whether you’re advanced, intermediate, or just starting out!  The Fazioli concert grand piano model F308 includes a fourth pedal to the left of the traditional three pedals. The lowest bass notes on the piano are a single thicker string. For a reference describing the lack of sostenuto pedals on European pianos as of 1982, see Good 1982:22.  The moderator, or celeste mechanism used a layer of soft cloth or leather between hammers and strings to provide a sweet, muted quality. This creates the illusion of loudness when really, the continuous vibration of the strings is creating a fuller or bigger sound. The Clementi piano firm was later renamed Collard and Collard in 1830, two years before Clementi's death. , Recent development in pedal configuration. The first way is with the “ped” and asterisk symbols. This is called overlapping pedaling, and it is how you create a continuous sound from the piano. Americus Backers' 1772 grand, his only surviving instrument, has what are believed to be original pedals, and is most likely the first piano to use pedals rather than knee levers. The pedal holds up only dampers that were already raised at the moment that it was depressed. They are more common on digital pianos as the effect is straightforward to mimic in software.  Johannes Zumpe's square piano, made in London in 1767, had two hand stops in the case, which acted as sustaining stops for the bass strings and the treble strings. " The damper pedal has the secondary function of allowing the player to connect into a legato texture notes that otherwise could not thus be played. Usually, the sostenuto pedal is played with the right foot.  A square piano built by Adam Beyer of London in 1777 has a damper pedal, as do pianos built by John Broadwood, ca. You may also choose to use it if you are playing your music in a quiet setting. It raises all the dampers off the strings so that they keep vibrating after the player releases the key. This is called overlapping pedaling, and it is how you create a continuous sound from the piano. Tre corda, literally meaning “three strings,” means to release the soft pedal, or resume allowing all three strings to sound. Pedal Markings in “I Giorni” by Ludovico Einaudi. The websites of Bechstein, Bösendorfer, Petrof, and Fazioli as of 2015 all describe their top-of-the-line instruments as including the sostenuto, and for Grotrian it is an available option. The stop was a knob on the side of the keyboard. Piano builders were quite creative with their pedal placement on pianos, which sometimes gave the instruments a comical look, compared to what is usually seen today. , The sustaining, or damper stop, was first controlled by the hand, and was included on some of the earliest pianos ever built. This is why sustain pedal inputs feature even on beginner level home keyboards. I've had my piano (a Bechstein if that's any help) for a while and it has this pedal that always seemed a bit odd to me. The sustain pedal removes the dampers from the strings, allowing notes to ring out for longer, even when the keys are not held down anymore.