# Nonlinear process A nonlinear process is one in which changes in the output are not proportionately linked to changes in the input. Most systems in nature are inherently nonlinear.[^1] We love saturation in part because it's imperfect, as I wrote about in [[Natural beauty is imperfect]]. Dynamics processing like compression and expansion are also nonlinear. Compression and expansion attempts to do nonlinearity without distortion.[^2] A system is linear if is both homogenous (output is proportional to input) and additive (e.g. a high-pass filter and low-pass filter = a band pass filter = a low-pass and a high-pass filter).[^3] Modulation and automation turns any linear system to a nonlinear system.[^3] [^1]: [Nonlinear system](https://en.wikipedia.org/wiki/Nonlinear_system) [^2]: [WTF is a Non Linearity?](https://www.youtube.com/watch?v=mytc7i0jm34) [^3]: [Meaning of System Linearity in Audio Production | Tokyo Dawn Knowledge Base](https://docs.tokyodawn.net/meaning-of-system-linearity-in-audio-production/)