This is a mixing program using Cmix.  There are four data cards:

open 

The program will mix the currently opened soundfile 0 into the currently
opened soundfile 1.  Opening another soundfile with cmix descriptor 0 or
1 will close the currently opened one.

reset (times per second)

This will set the number of times per second that the program will 
reinitialize the phrasing envelope curve.  The default is 200.

setline time1, amp1, time2, amp2, time3, amp3, ... timen ammpn

This will load an array with a curve proportionately described by the
time vs amp values on the card.  The time values are arbitrary in that
the entire curve will be squeezed into the array, and subsequent mix
commands will sample the curve once, no matter what their duration.
An instantaneous shift in amplitude can be specified by adjacent times
which are identical, but with different amplitudes.
 
mix  inskip, outskip, inend, amp, ch1loc, ch2loc etc.

This will actually read the input file beginning at time inskip, add it 
to the output file beginning at its time outskip, until time inend on the
input file.  If inend is specified as a negative number its absolute 
value indicates duration.  The signal will be multiplied by amp before it
is added to the output file, and input channel 0 will be placed in output
channel ch0loc, input channel 1 in output ch1loc etc.  A value of -1 for
chloc will force that channel to be skipped.