symptoms: sound was garbled when in laptop mode, but was relatively OK in tabloid mode. I could reproduce this in boot mode and therefore believing I had ruled out software.
changes: I just recently upgraded to kde pim pi 2.0.24 and I switched to the smaller battery. I switch to the smaller battery from time to time when I want a slimmer profile. The weather has also changed as there have been a few rain storms in the last couple of weeks (higher humidity) and warmer temperatures.
outcome: So far sound is back to normal. I can play music and alarms from any position with no sign of distortion. I have no idea what has happened, but maybe it will give hope for some of the other owners with similar problems. I hope this lasts at least until the end of summer when I hope to buy a new Z.