The manuscripts, copies of chorale fantasias for organ by Johann Adam Reinken and Dietrich Buxtehude, date from around 1700 and are the oldest yet found in the composer's hand, according to the BBC. They were discovered in an archive of Bach's music and other papers at the Duchess Anna Amalia Library.
The papers survived the 2004 fire that badly damaged the library because the Bach collection had been stored in an underground vault.
The two manuscripts are currently being shown at the library in Weimar; from September 17 they will be on display at the Bach Archive in Leipzig.