The modern piano, which largely took its current form between approximately 1790 and 1870, is a profoundly different instrument from its lighter 18th-century predecessors used by classical composers. Key innovations during this period included the development of a heavy cast-iron frame, ultra-tough steel strings, felt hammers, and an expanded pitch range, all contributing to a powerful tone and extended sustain. The prototype of this robust new instrument, exemplified by Steinway's acclaimed exhibition at the Paris exhibition of 1867, resulted in pianos that can weigh six times more than early models.

This dramatic evolution presents a significant challenge for musicians, as much of the iconic piano repertoire by composers like Haydn, Mozart, and Beethoven was originally written for instruments with a much lighter touch and different tonal characteristics. Consequently, there is an ongoing interpretive debate about performing earlier works on modern pianos, which has fueled a revival in the use of historically accurate instruments to capture the composers' original intent.