JS Bach was born in 1685; Ben Franklin in 1706. Franklin was younger by 21 years, maybe more or less depending on the actual dates.
Bach died in 1750, while Franklin died in 1790, 40 years later. Franklin lived a lot longer, and a few years moor recently than Bach, but to me it's useful to think of them together, as I imagine their costumes, which were very similar, except that Franklin never wore a wig.
Franklin is often described as a 'polymath', which is an old word that means 'a person with very diverse interests, skills and talents, what is also described as a Renaissance man. About Bach, we don't really know; we do know he was interested in music, and theology, but apart from those subjects, we don't know much about him.
We are told that he was interested in the design of organs; he was an excellent organist, and was hired as a consultant for at least one church that was having a new organ built.
Music, at that time, was a broad area of interest; there was composition, in several different forms; Bach was a master of many of these, and the Oratorio form extended into the area of drama. Bach could play almost any keyboard instrument, but also strings instruments: violin, viola, and very probably cello and double bass. He knew the theory of oboes and bassoons, and probably trumpets and horns, and recorders. Because of this wide range of expertise expected from a court musicians, there was very little time for one to explore other interests. We know Bach had s limited interest in local politics, because it impinged on his management of a small court orchestra that was expected of him.
Franklin was interested in writing, publishing, politics and political philosophy, he was an ambassador, he was involved in the independence movement, he was interested in science, and a host of other things. I can't even imagine the two men meeting, or even whether they would have had a common language of discourse. I can imagine that Franklin spoke French, having been the Ambassador to France. We are not told whether Bach spoke any language other than Deutch, and read a little Latin. And also perhaps a bit of Italian, because by Mozart's time many musicians could understand a little Italian.
Mozart, who was born two years after Bach died, could speak several languages fluently, certainly Italian. Mozart's entire life was within Franklin's lifetime.
Archie