What are three improvements that make the modern piano what it is today?

Three key improvements that define the modern piano include the use of a cast iron frame, which provides greater stability and allows for higher string tension, resulting in a more powerful sound. The introduction of felt hammers replaced the earlier wooden ones, enhancing the tonal quality and dynamic range. Additionally, advancements in scaling and string design have improved the instrument's overall intonation and sustain, making contemporary pianos more versatile and expressive.