The Crossfader works like a crossfader found on a typical DJ mixer. It allows you
to select a Line assigned to each side, and slide the fader to the left or right to
mix between the two assigned lines.
At the bottom of each line are two buttons:
When Punch-In is shown like in the above picture, the line is always audible; in
other words, it is routed directly to the output mix.
If you Mute a line, this section looks like the following:
Clicking on the buttons on either side will assign that line to the respective side of
the Crossfader:
In this situation, the line is assigned to the Right side of the Crossfader. Sliding
the fader to the left will cause this line to become inaudible.
The Crossfader has some buttons of its own:
Clicking the << and >> buttons cause the fader to AutoFade in that direction. You
can adjust the speed of this in the Options Dialog
.
Clicking the 
button swaps the two sides of the crossfader. This is useful if, for
example, the line assigned to the left side is physically to the right of the line
assigned to the right side; clicking this will cause the interface to make more
sense, to match the actual physical layout.
