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What
is digital
piano voicing?
Digital piano voicing is an attempt to
perform the same operations done by the piano tuner, but by working
directly on
the digital samples recorded from a real piano. It consists in three
stages: analysis, voicing and synthesis. Voicing and synthesis are
somewhat imbricated, in the sense that one has to listen to the result
and modify some parameters values until the resulting sound gives
satisfaction.
First stage: analysis
The
first stage consists in analyzing each recorded sample. This task is
done by using a combination of Fourier analysis
(FFT) and Prony analysis (equivalent to Padé analysis), which is
particularly devoted to analysis of signals of the form
a(t) = sum ck exp(-dk t) sin(2 pi fk t + pk) ,
that is, consisting
in
a sum of overtones with respective
amplitude ck,
decay
rate dk,
frequency fk
and phase pk.
Second
stage: voicing
This
second stage is the core of digital voicing. It consists in modifying
the different parameters issued from analysis, in order to improve the
tone
quality and the eveness of the instrument. Parameters
dk,
fk
and pk
are
used for adjusting:
Parameters
ck
give the "color" of the sound, and their evolution from note to note
give the eveness of the sound. The voicing attempts to modify them as
less as possible, correcting however notes where overtones are too weak
or too strong with
respect to the global color of the piano. Listen to three different
voicings
of the same note:
Third
stage: synthesis
In this third stage, all components are
re-assembled by using the modified parameters issued from the second
stage. The result is a new collection of samples which can then
be played on digital instruments.
Here
are two exampes showing the result obtained by this digital
voicing technique:
Surely you will find
that there is still some work to be done ! More examples can be found
in section Sound examples.
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