This module works much like the adder and subtractor modules do, but
has an effect which is more like mixing two signals together and
adjusting their levels so they still remain within similiar value
ranges.

When the function parameter is set to sub, then in_modifier will be subtracted
from in_signal.

The bias parameter controls how much to balance the two signals.
Setting bias to 0.25 means 3/4 of in_signal will be heard, while only
1/4 of in_modifier will.

See also: adder subtractor muliplier
