A manuscript notebook by Mozart containing compositions and lessons he gave to the Duchesse de Guînes has been discovered thanks to the diligence of an employee at the National Library of France.

On February 2, François-Pierre Goy, who enjoys exploring unidentified musical manuscripts, selected an untitled notebook from a collection of 20 manuscripts he had decided to examine before his retirement, according to the music department of the National Library of France.

While browsing through the notebook, he was astonished to discover manuscripts by Wolfgang Amadeus Mozart (1756–1791). Their authenticity was later confirmed by experts, including specialists from the Mozart Library in Salzburg, Austria, the composer's birthplace.

Discovery of New Mozart Musical Manuscripts at the National Library in Paris (AFP).

The notebook contains around 12 “composition lessons” and daily exercises that the Austrian composer gave between May and July 1778 to Marie-Louise-Philippine de Bonnières de Guines, a talented harpist and daughter of the Duke de Guines, a renowned flutist, Goy explained.

Its 44 pages also include seven pieces for flute and harp, the last of which remains unfinished, the librarian told Agence France-Presse during a presentation of the remarkably well-preserved notebook.

The pieces will be performed for the first time on Sunday during the Fête de la Musique by musicians from the Radio France Philharmonic Orchestra at a concert hosted by the National Library.

The manuscripts will be displayed during the concert before being transferred to the National Library’s museum.

The compositions, which have a combined duration of approximately twenty minutes, will be broadcast on France Musique on Monday at 3:00 p.m. local time (13:00 GMT).