Can 'ploth' draw the dynamic set of functions?

[Yuri <yuri@rawbw.com>]

Tutorials usually have examples with a fixed function set, like this: 
ploth(X=1,2,[X,log(X)])

What if I need to draw the computed set of functions? This example fails:
ff=[X->X,X->log(X)]
ploth(X=1,2,ff)

Or in simpler case, can I draw the function f(X,N) = {sin(X*N)}, when X 
is an interval, but N is taken from the precomputed parameter array, so 
it will draw one graph per value in the parameter array?

Yuri