I have seen the following with real physical objects. I thought I could try to do this in Euler Math Toolbox (EMT). It is not exactly accurate since the frequency of the pendulum is inverse proportional to the square root of the length of the pendulum. But that does not really matter.

fr=(10:0.1:11)';
t=0:0.002:100;
x=sin(fr*t*2*pi);
function showx (x) ...
$ markersize(20);
$ for k=1 to cols(x);
$    plot2d(x[,k]',1:rows(x),
$       a=-1,b=1,c=1,d=rows(x),>points,
$       style="o#",color=green,<grid);
$    wait(0);
$    until testkey();
$ end;
$ endfunction
clg;
showx(x);