According to J.F.Agricola, Mr Silbermann told him that Bach tried one of
his fortepiani around 1735-36, and he (Bach) said that the timbre was nice,
but it was too weak in the high register and too difficult to play.  At
first, Silbermann was very disappointed, but this was a spur for him to
improve his instrument.

In 1746, both Silbermann and Bach were in Naumburg.  Silbermann told Bach
that his fortepiani were improved and that the previous year the King
Friedrick II liked them very much (he bought 15 of them).  The second (and
last) time Bach came across a fortepiano was in the presence of the king.

There is no evidence of Bach's concerti on such an instrument, and that
he liked it.  But since Bach is now considered as the greatest of all
composers, I can see why sometimes people try to open up a way through
history.

Roberto Strappafelci