The library's archives held the long-lost masterwork by Antonio Vivaldi.

One of the great composer's masterpieces is the opera Orlando Furioso from 1727, yet among Vivaldi's personal documents was a completely different score from 1714.

A new version of Vivaldi's opera Orlando Furioso has been found, 270 years after his death, the library's archives held the long-lost masterwork by Antonio Vivaldi in a discovery dubbed by music experts as "a bombshell in the realm of Baroque opera."

Thirteen years before Vivaldi created his famous masterwork, in 1714, the manuscript was discovered. The manuscript was discovered in Vivaldi's personal collection in the Biblioteca Nazionale in Turin. A young Bolognese composer named Giovanni Alberto Ristori's composition had somehow been categorized as a reworking of an already-existing Orlando Furioso. It includes up to 20 previously unheard arias that were all written at the same time that Vivaldi was working on The Four Seasons, widely regarded as the most recorded piece of classical music in history. The discovery occurs as Max Irons is reportedly set to feature in a significant movie on the composer's early years. There are multiple Vivaldi biopics under development.

Orlando said: "Vivaldi created two Orlando Furiosos, which is astounding in the realm of Baroque opera as well as for what it says about him as a composer to work on a libretto before returning to it and working on it once again. Nothing like this was anticipated."

The "new" Orlando will have its global debut on July 20 at the Festival de Beaune before being recorded by the French label Nave for publication in November as part of their Vivaldi Edition series.