Who had used Sox knows that it's reliable, quite featured, and very simple to use for common tasks. Rubberband also works fine through Traverso. Problem is that the present whole-wave implementation of External Processing is too basic, and makes it unusable for most practical purposes.

At the very least, it should be done clip-wise. That is, extract the exact clip portion of the wave, apply the effect to it, and make a new clip from that, to replace the old one. The new wave, behind the new clip, would be just as extense as the new clip.

Perhaps further future evolution could present to the user some sort of shortcuts for some useful Sox commands (pitch correction, mix to mono, wave inversion, time stretching, even noise cleanup, ...). For example, in the form of additional tabs in the EP window.

In an even further evolution (and with more coding involved, true), some of the above functionality could be offered in the form of plugins, using available static libraries (libSox, or Rubberband libraries...).

Keep the good work :-)
JC