A handwritten serial number inside a neglected 1807 Broadwood square piano inspired this illuminating story of an almost-forgotten musical instrument that transformed the musical and cultural perceptions of the western world. Square pianos were the first popular pianos, and the core of the classical piano repertoire—Mozart, Haydn, Beethoven—was written for such early pianos. This absorbing history leads back to the early days of the Industrial Revolution and the birth of mass production, commoditization, and global distribution of pianos from the ports of London to the shores of America and around the world. Both an investigative story and genealogical study that highlights a key period in music history, this chronicle closely examines the roles of John Broadwood—the most successful piano maker in late-Georgian London—and of one of his professional customers, Mr. John Langshaw, an organist and music master.