A nearly 300-year-old musical manuscript housed at The Carnegie Library contains what is believed to be the earliest examples of Johann Sebastian Bach's handwriting, officials said Tuesday.

The work is an organ prelude and fugue in G minor by the German composer Dietrich Buxtehude (1637-1707), given to the main Carnegie library in 1895.The three-leaf manuscript, a copy of the Buxtehude piece by Bach and his older brother, Johann Christoph, was not authenticated until recently by Hans-Joachim Schulze, the director of the Bach-Archive in Leipzig, Germany.

The manuscript, with writing on both sides, is viewed by scholars as important in the understanding of the early musical development of Johann Sebastian Bach (1685-1750).