Its probably something to do with the control having to be inside the same loop as what it
is controlling. And yes, normally putting high-cost fx’s such as echo outside of loops is preferred,
especially when the loop has a low sleep time… but every rule has its exception I guess, and I
dont think a filter such as :rplf is really high cost.
Please continue to work on this, I was a huge Herbie fan back in the day. 
Eli…