In the context of computer music, the control of spectral envelopes offers the possibility to influence the timbre of a sound to a great degree, allowing composers to obtain a desired effect or characteristic of a sound by the use of a flexible, unconstrained representation (the spectral representation gives complete freedom to modify a spectral envelope in any way). To the performer, the possible real-time application of spectral envelope manipulation would greatly enhance expressivity through easily understandable and ``musical'' parameters, i.e. parameters that pertain to a model (the source-filter model) which is valid for many instruments.
Between the creation of completely new sounds and the modification of existing sounds lies the combination of features of different sounds. For example, cross synthesis with spectral envelopes crosses the characteristics of two distinct sounds: The partial structure is taken from one sound, and the spectral envelope from another.
However, the application of the methods and tools developed in this project will not only enrich musical creation, but also the demands of art will in turn influence further research conducted on this topic:
Whenever I asked computer music composers and performers what they would do if they had the possibilities to manipulate the spectral envelope of sounds, they inevitably came up with ideas about varying spectral envelopes in time.
For a worthwile artistic application, we have to raise our point of view above the one-dimensional perspective adopted in most of this project, in that the richness and complexity of sound--which is an inherently time-based phenomenon--were only viewed through the keyhole of one time-frame.
Alas, this is out of the scope of this project. Here, the mechanisms for effecting these changes have been developed, the question how to apply and control them has to be answered elsewhere.