Elektron Musical Instruments

> is there any way to set the length of each instrument track on the MD
> to a different length?

no, each track has the same length.  yes, it would be cool if they were of
different length. but I think the main reason for "why not?" would be that
I don't believe that either machine was designed that way. thus working it
into the interface would prove to be less than ideal - and we all know
that Elektron values the ease-of-use and immediacy of their interfaces. 
so that would be my guess....