According to Johann Forkel who penned the first biography of Bach in 1802, “In musical parties, Bach took pleasure in playing the viola. With this instrument he was in the centre of harmony, whence he could best hear and enjoy it on both sides."
Bach understood the potential of the viola. In his orchestral works, the viola part is as important as the other string parts. In the 6th Brandenburg Concerto, the violins are completely absent.
There is much speculation as to why Bach chose to omit the violin from this and other works. One theory is that Bach wished to upset the musical status quo by giving the violas, typically played by servants and other “lesser” individuals, a more important role.
I cannot help but be proud of the fact that my favorite composer, way back in 1721, was a proponent of equal rights!