Around 1720, how many Brandenburg Concertos did Johann Sebastian Bach compose altogether?

In 1721, Johann Sebastian Bach presented a beautifully bound manuscript to Christian Ludwig, the Margrave of Brandenburg-Schwedt. This collection, which Bach titled "Six Concertos with Several Instruments," was essentially a musical job application. Bach had met the Margrave two years prior and was likely hoping this impressive portfolio would secure him a position in the Margrave's court in Berlin (Review). The dedication is how the set of six concertos eventually earned the famous name we use today.

Ironically, this grand gesture seems to have gone unnoticed. The Margrave likely never had the concertos performed, as his small court orchestra couldn't handle Bach's demanding and varied instrumentation. Each of the six pieces is written for a different and often unusual combination of solo instruments, from horns and oboes to the viola da gamba and the high-pitched trumpet. They were a brilliant showcase of Bach's compositional genius, but perhaps too ambitious for their intended recipient.

For over a century, the manuscript lay forgotten in the Margrave's library. The concertos were not published until 1850, long after Bach's death. Since their rediscovery, these six works have become some of the most celebrated and frequently performed pieces of the entire Baroque era, representing a pinnacle of the concerto grosso form and a testament to Bach's enduring mastery.