Richard Todd wrote:

>My impression was that the Art of the Fugue was not written "for" anything
>in particular.

Well, research shows that it was a keyboard work, written in "open score",
as this is called.  In the past, when people noticed that no instruments
were specified, and when they believed that all the composers wrote for
posterity, AoF was regarded as a great example of an abstract work.
Current research sees it differently.

-Margaret Mikulska