Fader applies a repeating volume envelope
to the sound passing through it.  This
envelope is visually displayed as a 
volume-vs-time graph.

Clicking within the display area with
the left button will create a new fade
point.  Fade points can be moved by
dragging with the left button, and
removed by clicking with the right.
The display shows how the volume will
be adjusted, continuously from the 
volume at one point to the volume of 
the next.  

The fade pattern will have a certain
length, expressed as a number of beats.
If the tempo of the sound is unknown,
then 60 bpm is assumed (one beat per
second.)  Pressing the 'synch' button
will align the fade pattern such that
the edge of the display falls on a
beat.  Note that if the underlying 
source is nudged by a fraction of a 
beat, this alignment will be lost.

The fader has an additional mode which
makes it easy to vary a simple on-off
pattern.  Toggling the 'perf' button
will replace the current fade points
with a pattern which fades from zero
to full volume and back again, with 
the peak centered at the edges.  While
in perforate mode, the peak width and 
base width can be adjusted to control
what portion of the sound is loud.

When a fade pattern is created,
it is started in synch with the song
such that the endpoints of the fade 
pattern fall on a beat.  However, if 
the underlying source is nudged, the
fade pattern will no longer be in
synch.  Pressing the 'synch' button
resynchs the pattern.