A large portion of Bach's orchestral music is today considered to have been lost for ever. Fortunately the concerto for two violins, or double concerto, has survived - though only just. It was found among the papers of his son CPE Bach along with the A minor violin concerto and first published in 1874, over a century after the composer's death.
Bach was amazingly prolific, but even he had to recycle ideas sometimes. There is also an arrangement of this work for two keyboards and strings, perhaps reflecting a Saturday when he was just a little too busy to make the composing deadline for his weekly music concert with a genuinely new work. It was probably written at C