Hello Steve.  There is one guy at the Raspberry Pi Foundation who is aware of the problem and is going to try to get around to trying to fixing the sound driver.  But as it is not broken for most applications and only seems to badly affect this accessibility issue I guess it is low priority.  Personally I think using the GPU directly for tts is a good idea anyway as I have had all kinds of problems with ALSA and pulseaudio in the past

I'm now working on an Emacspeak server and then a speech-dispatcher module which also use my code library.

I think speech-dispatcher might already be ok but I suspect it is because the sd espeak module has the audio chunk size set so high that the stuttering doesn't occur but it eats up RAM as a result.  My audio library is much leaner

I'm going to try to come up with an alternative to speech-dispatcher which will interface to Orca and run in a much smaller footprint.