6. Manipulation of Spectral Envelopes

This chapter describes the different types of manipulation that are possible with spectral envelopes. If not said otherwise, it is assumed that the spectral envelopes are in the form of the canonical spectral representation described in section 4.3.

  

Figure 5.1: General manipulation of spectral envelopes

  

Figure 5.2: Interpolation, the most important type of manipulation of spectral envelopes. The resulting spectral envelope will be a weighted average of the two input spectral envelopes (termed the original spectral envelope and the target spectral envelope).

Manipulation  is at the heart of the creative process. It allows composers and musicians to surpass what is given in recorded sounds, either to create sounds which are far from the original, or to subtly modify given sounds, or to mix characteristics of different sounds. By manipulation, a spectral envelope is changed according to some parameters, as depicted in figure 5.1. The most important type of manipulation, interpolation between spectral envelopes, is described in section 5.1, manipulations changing the amplitude of a spectral envelope are covered in section 5.2, other types of manipulations in section 5.3.