Rebody : Sample Matrix

For each of the 12 clips (i.e. each line in the matrix) a different parametrisation has been chosen. The parameters concern the degree of projection of the 12 2D points onto a circle (circ) and the synthesis of the sound texture.

In total there are 26 sound texture parameters. For all, parameter default values are defined. A texture with all parameters at their default values would be silent. For each clip a sound texture has been composed using between 6 and 14 parameters out of the 26. The parameters unused in a clip assume their default values.

There are parameters concerning the analysis of the 2D points (prefixed sp, for speeds). The instantaneous and averaged speeds of the 12 2D are estimated and mapped according to their ranges (minimum and maximum values in the clip) and an exponent, allowing for a compression or expansion of the speed dynamics. The parameter sp.wind specifies the number of 80 ms frames over which the speed is averaged. Only values of 10 or 50 frames (0.8 and 4 s) are used. The averaged speed values are centred with respect to the analysis window, i.e. the averaged values anticipate changes.

The parameters sp.inst and sp.mean specify the mappings for the instantaneous and the averaged speed, which may control the synthesis parameters (see below). The 5 values are: exponent, minimum and maximum speed (input range) and minimum and maximum of mapped speed (output range). The mapping function linearly maps the exponentiated current speed from the input range (computed from the exponentiated minimum and maximum) to the output range.

There are three other groups of parameters concerning the sound synthesis and corresponding to the three aspects of the synthesis model (prefixed cl, for clicks; co for comb filters; vo for vocal formants). Some of them are fixed and others can be modulated according to the analyses of the 12 2D points and the appearance or disappearance of lines drawn between them.

The modulatable parameters comprise of their second set of values and mapping specification consisting of 4 components (values between 0 and 1, adding up to 1). The 4 components specify the relative influence of 4 aspects of the current figure on the sound. The 4 aspects are offset, instantaneous speed, averaged speed, and line appearing or disappearing. The 4 components can be freely mixed. Consider the following examples: (1 0 0 0) means a fixed (i.e. no) modulation; (0 0.5 0.5 0) means 50% of instantaneous speed and 50% of averaged speed modulate the parameter; (0 0 0 1) means that the parameter is modulated when a line appears or disappears; (0 0.8 0 0.2) means that 80% of the instantaneous speed and 20% of a line change modulate the parameter.

Modulatable parameters must specify a range in which they can be modulated. This is usually an interval (cl.off, cl.cutoff, cl.rq, co.decay, vo.octave, vo.stress). Level parameters (in dB, postfixes out, rev1, and rev2) also have a third value, which is a level offset. The pan parameters (cl.pan, co.pan, and vo.pan) take values between 0 (indicating no panning) and 1 (full amount of panning depending on the 2D point’s relative horizontal position in the bounding box of the figure). Frequencies are specified in MIDI pitch (cl.cutoff).

If a parameter has two sets of values, then a linear interpolation between these sets is performed between the beginning and end of the clip (i.e. half way through the interpolation is at 50%).