The toy piano is a musical instrument, made as a child's toy, but which has also been used in more serious musical contexts. The instrument was invented in Philadelphia in 1872 by a German immigrant named Albert Schoenhut.
It is in the form of a scaled down model of a piano, usually no more than 50 cm in width, and made out of plastic. The first toy pianos were made in the mid-19th century and were typically uprights, although most toy pianos made today are models of grands.
Rather than hammers hitting strings as on a standard piano, the toy piano sounds by way of hammers hitting metal bars or rods which are fixed at one end. The hammers are connected to the keys by a mechanism similar to that which drives keyboard glockenspiels. This makes it sound more 'tinkly.'
Toy pianos ostensibly use the same musical scale as full size pianos, although their tuning in all but the most expensive models is usually very approximate. Similarly, the pitch to which they are tuned is rarely close to the standard of 440 Hz for the A above middle C.
A typical toy piano will have a range of one to three octaves. Some cheaper models may not have black notes, meaning they can play the diatonic scale (or an approximately tuned version of it), but not the chromatic scale.
Although primarily thought of as a toy, the toy piano has been used in serious musical endevours. The most famous example is the Suite for Toy Piano by John Cage. Other works in classical music for the instrument include Ancient Voices of Children by George Crumb and a number of pieces by Mauricio Kagel. In improvised music, Steve Beresford has used toy pianos (along with many other toy instruments).
In 1997 the pianist Margaret Leng Tan released the record The Art of the Toy Piano. On it, she plays a number of pieces written specially for the toy piano as well as arrangements of other pieces, including Ludwig van Beethoven's Moonlight Sonata and The Beatles' "Eleanor Rigby".