Young Blonde Girl Wearing A Necklace At The Piano

In 1863, Henri Fourneaux invented the player piano, which plays itself from a piano roll without the need for a pianist. A performance is recorded onto rolls of paper with perforations, and the player piano replays the performance using pneumatic devices. Modern equivalents of the player piano include the Bösendorfer CEUS and the Yamaha Disklavier, using solenoids and MIDI rather than pneumatics and rolls.
A silent piano is an acoustic piano having an option to silence the strings by means of an interposing hammer bar. They are designed for private silent practice.
The transposing piano was invented in 1801 by Edward Ryley. It has a lever under the keyboard used to move the keyboard relative to the strings so that a pianist can play in a familiar key while the music sounds in a different key.
The prepared piano, encountered in some contemporary art music, is a piano with objects placed inside it to alter its sound, or that has had its mechanism changed in some other way. The scores for music for prepared piano specify the modifications, for example instructing the pianist to insert pieces of rubber, or paper, or metal screws or washers, in between the strings. These either mute the strings or alter their timbre.