Of all the problems offered by Bach's keyboard works, that of choosing
the proper instrument is probably the most far-reaching. Nothing is more
important to the inner spirit of a performance than the aura, the atmos-
phere created by the instrument. Our examination of the various types of
Bach's keyboard works has shown that almost every piece displays in its
structure, as if written with invisible ink, the stamp of its instrumental
destination; indeed, this is done with such a degree of clarity that a
musician of the period would have had no difficulty in understanding the
message. Might it be possible that a similar situation exists in regard to
the problems of dynamics, tempo, ornamentation, and articulation; that
for the solutions of these problems, too, we need only to make the
"invisible ink" readable?

In the case of dynamics, the answer can be given immediately in the
affirmative. Although only a small number of forte and piano signs in
Bach's own hand have come down to us, and although most of them, as
we know from the previous chapter, are nothing other than indications
for registration, the instruments themselves reveal Bach's intentions with
infallible clarity. We need therefore not wonder that he found it
unnecessary to provide us with more detailed information.

For pieces written for the harpsichord, problems of dynamics are
practically nonexistent once we have chosen the proper registration. The
number of sound levels will correspond to the number of terraces to be
used. As we have said before, short pieces, especially dance movements,
do not need more than one tone color from the beginning to the end; in
other cases the normal number of terraces is two: single tone and tone

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