To enable the use of these techniques in a common mixing situation, we’ve made some example configurations in Reaper. The idea is to extract some feature of the modulator signal (using common tools like EQs and Compressors rather than more advanced analysis tools), and use this signal to affect the processing of another signal.
By using sidechaining we can allow the energy level of one signal to gate/compress/expand another signal. Using EQ and/or multiband compression on the modulator signal, we can extract parts of the spectrum, for example so that the processing will be applied only if there is energy in the deep frequencies of the modulator signal. Admittedly, this method is somewhat limited as compared with a full crossadaptive approach, but it is widely available and as such has a practical value. With some massaging of the modulator signal and creative selection of effects applied to the affected signal, this method still can produce a fairly wide range of cross-adaptive effects.
By using automation techniques available in Reaper (we will investigate how to do this in other hosts too) , we can map the signal energy directly to parameter changes. This allows cross-adaptive processing in the full sense of the term. The technique (as implemented in Reaper) is limited by the kind of features one can extract from the modulator signal (energy level only) and by the control signal mapping being one-to-one, so that it is not possible to mix several modulator sources to control an effects parameter. Still this provides a method to experiment easily with cross-adaptive mixing techniques in a standard DAW with no extra tools required.
Sidechaining used in an unconventional cross-adaptive manner is demonstrated in the CA_sidechain_pitchverb Reaper project.
Signal automation based on modulator energy is demonstrated in the CA_EnvControl Reaper project
Modulator signal: The signal being used to affect processing of another signal
Affected signal: The signal being modulated