A new Stravinsky work arrives in Australia at the end of June, the first in many decades. In fact, his Funeral Songis over 100 years old, but the score was lost for most of the 20th century and only came to light in 2014. The find was a major discovery, but just one of many in recent times, with intrepid librarians and researchers around the world regularly identifying long-lost manuscripts. So how does music by the great composers so often disappear? And where should we be looking for the next long-forgotten masterpiece?

The most famous rediscovery was of the Haydn Cello Concerto in C Major, which made a triumphant return to the repertoire in 1962 with a performance in Prague by cellist Miloš Sádlo conducted by Charles Mackerras. Haydn wrote the concerto in the early 1760s, early in his employment by the Esterházy family, and it was premiered by Joseph Franz Weigl, principal cellist in the Esterházy orchestra. The concerto appeared in a thematic catalogue that Haydn drew up of his own works, but for almost two centuries the music itself was thought lost.

Then, in 1961, Oldřich Pulkert, archivist at the Prague National Museum, discovered...