Adagio - Johann Sebastian Bach -

The most famous "Bach Adagio" is actually an arrangement. Around 1715, Bach transcribed an oboe concerto by the Venetian composer Alessandro Marcello for solo keyboard.

Bach added intricate, "filigree" ornamentation—turns, trills, and passing notes—that transformed a straightforward tune into a masterpiece of Baroque expression. Adagio - Johann Sebastian Bach

Marcello’s Oboe Concerto in D minor featured a simple, singing melody. The most famous "Bach Adagio" is actually an arrangement