Most modern piano strings are made from high-quality steel, chosen for its strength and durability. Steel strings are capable of withstanding high tension, which is essential for producing the rich and resonant sound pianos are known for. The strings vary in thickness, with the lower notes requiring thicker strings to produce deeper tones, while the higher notes use thinner strings for clarity and brightness. In the lower register, the steel core is often wound with copper to add mass without significantly increasing tension. This combination allows the piano to cover a wide range of pitches, from the low rumble of the bass to the sparkling highs of the treble. The use of steel strings, along with a robust wooden frame, was a crucial development in the evolution of the modern piano, enabling it to achieve greater volume and expressiveness, qualities that have made it a central instrument in both classical and popular music.