A Wolfgang Amadeus Mozart composition for a string trio, long believed lost or destroyed, has been discovered at a library in the German city of Leipzig, researchers say. Written in the 1760s, probably in the composer’s early teens, the 12-minute composition was performed, in what may have been a 260-year-late premiere, in Salzburg, Austria, yesterday (September 19), Agence France-Presse reports.

The manuscript is believed to be a copy, made in the 1780s, of Mozart’s original transcription. Archivists discovered it while compiling the latest Köchel catalogue of Mozart’s works, which refers to the piece as Ganz kleine Nachtmusik; researchers know of many undiscovered chamber-music compositions by Mozart, due to a list compiled in the composer’s lifetime by his father. It is the latest of about a dozen Mozart works to be unearthed in modern times.