Research on the economic history of copyright and music publishing turned up an unusual source of data on the value of copyrights, namely detailed accounts of public auctions of musical items that were held in London between 1794 and 1960 of, inter alia, copyrights and the engraved plates from which musical works were printed. The standard contract between song writers/composers and music publishers in the 19th century bought out all rights and therefore the sale of the plates was also the sale of the copyright to the work, enabling the new owner to print and distribute the work. The sales also facilitated entry into and exit from the industry. This paper describes the historical circumstances of copyright and the market for printed music and presents some of the more notable data, with calculations of their present day values. Though insufficient for a full statistical analysis, the paper provides some hard evidence of the asset value of copyright in musical works as perceived by the music publishers of those times. The paper also suggests a basis for further research