| Résumé |
Synthesizer music performance requires precise control over sound
synthesis. Such a control necessitates a powerful sound synthesis
engine that faithfully models the sound properties and reacts to the
input commands in a realistic manner.
Achieving such synthesis is not an easy task. Most of studies in
instrumental sound deal with timbre of isolated sounds recorded in
"laboratory" conditions, thus having practically fixed pitch and
limited dynamics. The problem of expressive synthesis requires to
deal with a much wider range of sound's behaviour, so called
expressive inflections. One must understand the nature of sound's
behaviour in a variety of playing conditions and be able to quantify
the changes of spectro-temporal parameters in relation to the
expressive events. These new questions are idiomatic to the specific
instrument (involving subtle sound properties such as noise or
"texture" of a sound), and may-be even related to the style of playing
by a specific performer. As such, these questions usually are not
considered to be in the "timbre" domain.
In this work we present analysis of sound behaviour as it occurs in
course of an actual performances in several solo works. The following
parameters are investigated:
1. The amount of spectral envelope variation characterized by the range
and the rate of change.
2. correlation between pitch, energy and spectral envelope variations.
3. phase coherence as function of dynamics and pitch.
4. detection and segmentation of typical temporal patterns in time.
This includes both quick spectral changes during an attack and longer
spectral envelope evolution during the sustained portion of the sound.
5. presence of periodic and noise components, and specifically
detection of pitch correlated vs. uncorrelated noise.
The final goal of this study is to provide both quantitative and
qualitative representation of the expressive variations in sound and
thus define a suitable parameter model. This expressive model will be
further used in conjunction with the input controller, so as to
achieve a proper mapping between the human controls and the synthesis
parameters.
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