Using PARAMETERS, you can specify the frequency
(F) and the phase (P) of all four pendulums in
a harmonograph.

The parametric equations you are adjusting are:

     -rt
X = e   [sin(F t + P ) + sin(F t + P )]
              1     1         2     2
     -rt
Y = e   [sin(F t + P ) + sin(F t + P )]
              3     3         4     4

where:  r = damping factor, t = time
        F = frequency,      P = phase angle

The four pendulums in a real harmonograph
control the X and Y motions of the paper and
pen.