Limits the incoming signal with a tanh function.

Essentially computes output = tanh(input * gain). As the input signal approaches one or negative one it is soft clipped, the gain value helps push the signal up to the limits:

On this graph x is the amplitude of our input signal. You can see that as x increases y approaches one and can never exceed it.

As a result tanh limits the signal and can even be used a a wave shaper to distort, for example, a triangle wave into a sine shape.

Input	Description
unit input	The signal to limit.
gain	Additional input gain to push against the function.