Mozart's Fortepiano, housed in the Mozart Museum in Salzburg.
In the 1780s, a new keyboard builder arrived in Vienna. His name was Anton Walter, and his fortepianos had a greater dynamic range and a superior sound to previous instruments.
Mozart had also moved to Vienna, from Salzburg. He married Constanze Weber in St Stephen's Cathedral in 1782, and they had rented an apartment near the cathedral. Mozart was quite successful at this time and could afford a good piano of his own. So sometime after he had found a place of his own, he went to Walter's showroom and bought one of the fortepianos there.
Until the 1780s, Mozart had praised the fortepianos built by Stein. They came with knee levers for sustaining sound, which meant that the hands were free to play uninterrupted on the keyboard, and the sustaining action was undertaken by the knees - in the same way that we pedal with our feet.
But Walter's instruments in the 1780s still had hand levers (or 'stops'). Would Mozart have thought this was a restriction and a drawback? Interestingly, his own Walter piano (shown above) has knee levers. There are two levers, one for the right knee (this sustained notes in the upper register only) and another operated by the left knee (which sustained all notes on the keyboard). Did Mozart request Anton Walter to add these knee levers upon purchase? If not, and this Walter piano originally had pedals operated by the hand only, it means that Mozart's keyboard works from 1782 until his death would have been created with either very little pedal in mind, or occasional blurring of sound. This fortepiano underwent an overhaul in 1800, almost ten years after Mozart's death, and it is possible that the knee-levers were added then.
As well as buying the fortepiano from Walter, Mozart also purchased a 'pedal piano'. This was a keyboard which was played by the feet, and it fit under the keys, as on an organ. This provided a way to sustain lower notes if needed. Whether or not his Walter piano had knee levers, it is clear that Mozart most certainly wished to sustain certain harmonies, without the blurring or abruptness caused by hand pedals (or stops).
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He often took the instrument with him for performances in Vienna, where he lived until his death in 1791. Mozart's father, Leopold, wrote to his daughter, 'Since my arrival in Vienna, your brother's fortepiano has been carried at least a dozen times to theatres or some other house'.
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Even though we may learn something from hearing or playing Mozart's piano works on his own instrument, we will never know how it actually sounded, due to the modifications in 1800. Walter pianos evolved quite rapidly to suit the music market, and the one Beethoven owned was very different from Mozart's piano.
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An interesting note: Mozart rarely referred to his instrument as a 'fortepiano'. As was often the custom of the day, he called it a 'cembalo' - or 'cembalo con martelli' (with hammers). A harpsichord was a 'cembalo con penne' (cembalo with quills).
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