It worked!  Thanks so much.  When you said "Class method"/"Instance method", the light flickered on.

Now to make it do what I want it to do.  But that's another story...
> Hi Ted,
> 
> say
> 	def S2hhmmss.to_hhmmss(duration)
> 
> instead of
> 	def to_hhmmss(duration)
> 
> and it should run.
> 
> This defines a class method as opposed to an instance method.
> 
> Juergen
>