Standard linear crossfader with two inputs, used to mix between 2 audio (or control) signals with an adjustable transition.
When Fade mode is gain, this node performs a per sample linear interpolation: A * (1 - alpha) + B * alpha.
A * (1 - alpha) + B * alpha
When Fade mode is filter, a center frequency between 10 Hz and 22 kHz, based on the alpha setting is determined. A low-pass filter with this frequency is used on A, and a high-pass filter with the same frequency on B.
Note: Audio and Control lines (visualized with blue and purple, respectively) are both analogous to an analog signal. They can be used interchangeably, and, for example, an Audio output (blue) can be connected to a Control input (purple), or vice-versa.