Mutation Synthesis

Seth’s note: When I developed Mutation Synthesis while teaching at Cogswell Polytechnical College I was aided by three very bright students, Patty Liu, Doug Wright, and Walter Davies. Walter did a really nice write-up on the theory and possibilities of Mutation Synthesis, which I have included below. I still have no idea what “Boolean” means, Walter.)

MUTATION SYNTHESIS
1. Basic Theory. Mutation Synthesis utilizes at least two sound sources (“operators”) and rapidly alternates (“switches”) among the sources to produce complex spectral output.

2. Mutation.
Mutation is defined to occur when the operators switch at a rate faster than the length of the input waveform of at least one of the operators. Simple Mutation Synthesis utilizes two static sound sources as its operators. Complex Mutation Synthesis utilizes three or more sound sources that can be serial, parallel, or random switched. Serial Switching continuously switches operators in a linear order (ex. 1,2,3,1,2,3. . .) Serial Switching does not allow temporal overlap of operators. Parallel Switching continuously switches operators at one rate per operator, allowing temporal overlap of elements. Random Switching takes the above and adds elements of randomness to them. For example, Random Open Serial Switching switches operators in order at a random rate whereas Random Closed Serial Switching switches operators in order at a random rate within a specified domain. Random Parallel Switching would work in much the same way.

3. Modularity.
Static Mutation should produce static results. Dynamic Mutation is Mutation with time-varying output spectra. Dynamic Mutation is defined as changing the Activation Period (AP) and/or the Frequency of Mutation (Fm) over time. AP is similar to the grain time in Granular Synthesis, which is the amount of time that a single sound “grain” is of non-zero amplitude. Since the amplitudes of operators in Mutation Synthesis are Boolean, rather than ramped as in Granular Synthesis, AP is the time that an operator is “on” after being triggered. Frequency of Mutation (Fm) is then the frequency that an operator is switched “on.” Combining AP with Fm and varying their respective time and/or rate will produce dynamic output spectra.

4. Further Modularity.
The modularity section above deals with changing the defined parameters of Mutation Synthesis in real time to achieve dynamic spectra. Further dynamism occurs by mutating dynamic source signals with or without actual Dynamic Mutation. For example, changing the pitch over time of one or more of the operators’ source signals without changing the AP or Fm will change the wavelength passed through the operator. To illustrate: if the source signal’s frequency is ramped up by two octaves over an arbitrary number of APs and one quarter of the source wavelength passes during the initial AP, by the time the frequency ramp maximizes, two complete cycles of the source wavelength will pass at the same length of AP. The AP will then begin and end at zeroes without amplitude ramping (e.g., Granular).

Copy write 1995 Walter Davies Mutation Synthesis copy write 1995 Seth Clark, Walter Davies, Patty Liu, Doug Wright