A player piano is a type of piano that plays music automatically without the need for a human pianist. It uses a system of punched paper rolls or digital files to trigger the keys, allowing it to reproduce music accurately. This invention became popular in the late 19th and early 20th centuries, providing entertainment in homes and public spaces. The mechanism inside a player piano consists of a series of pneumatic devices that respond to the holes in the paper rolls. When air passes through these holes, it activates the corresponding piano keys, creating sound. Player pianos were a significant development in music technology, paving the way for modern automated instruments.