I just recently rewrote the code to include the second step, the volume adjustment. Then I noticed it was not working properly.

Thanks for the guidance Lyndell. I'll look at the links and try to figure this out. One quick potentially stupid question -- I'm unclear if I'm using the serial port in asynchronous vs synchronous fashion. Most of the commands I use are straight from the pronto developer guide (eg s.match("MV?\r", "\r", 250)). Is one method preferable to the other?