Just a note to myself that when I use the Command Performance tool in Bars and Pipes to talk to another Amiga program via ARexx, I need to make sure the "ARexx Port" in the tool is entirely capitalized. Otherwise, it will silently fail to communicate with the target.
In my screenshot, Command Performance will tell Sample Wrench to play the sample in the 'default editor' (the last editor window I clicked on), which is editor 0, with no transposing.
Also worth mentioning is one process for doing ARexx debugging: run a Rexx script which opens its own ARexx port and responds to commands. An example is given at Amiga.org. Also make sure to run
TCO, the ARexx console output utility. When done, you can close that console using