In 1940, American composer John Cage invented the 'prepared piano' to solve a practical problem. He was asked to write music for a dance performance in a space too small for a full percussion ensemble, but large enough for a grand piano. Cage decided to turn the piano itself into a percussion orchestra by placing objects—such as screws, bolts, pieces of rubber, and felt—directly between the strings. These objects alter the timbre of the notes, making them sound like metallic gongs, wooden blocks, or thudding drums. Cage provided precise 'instructions for preparation' for each piece, specifying exactly which string should be prepared and at what distance from the bridge. This transformed the piano from a harmonic, melodic instrument into a 'multi-timbral' percussion machine. His work 'Sonatas and Interludes' remains the most famous example of this technique, showcasing a wide palette of sounds entirely produced by a single piano.