From the notes on the YouTube site:
In March of 1721, Johann Sebastian Bach carefully inked six of his best concertos into a book for the Margrave of Brandenburg, Christian Ludwig. The original title, "Six Concerts à plusieurs instruments" is now known as the "Brandenburg" Concertos in English or "Brandenburgische Konzerte" in German.
These six concertos represent the summa of chamber music in the high baroque period, and the third concerto (BWV 1048) is noted for its rich texture of three violins, three violas and three cellos, with a continuo part for the harpsichord and violone.
Picture: Portrait of Johann Sebastian Bach by Haussmann, 1746
Courtesy of Wikimedia commons