Some time ago artrag mentioned a voice converter he had created that ran on the MSX and produced really nice voice at 60Hz. He was kind enough to adapt it for the PSG in the TI-99/4A and ColecoVision, and after lots of work-induced delays, I've put together a small package for those interested in using it.
With only three voices, the results are not quite as nice as the MSX, but most voice is still quite legible. I've posted a sample YouTube (it's just a quick and dirty test, but it demonstrates both good samples and not-so-good samples, so you can hear the range.) (Sample is running on a TI-99/4A, but the ColecoVision results are the same.)
Playback takes very little CPU (just unpacking 6 bytes per frame) and a fair amount of memory (360 bytes per second). It's quite good for adding short voice samples!
The actual converter runs under Matlab so requires the Matlab runtime and 64-bit Windows to execute. Alternately, the Matlab script is included so you can run it on your choice of platform if you have the ability to run Matlab scripts. I experimented with Octave and although it didn't run out-of-the-box, I eventually got an early version processing there.
For playback, I've included assembly playback code for both the TI-99/4A and the ColecoVision (the ColecoVision code is hand-optimized from SDCC output and runs fine linked into C programs). There's also a VGM converter with C source in case you have a need to VGM audio files (for instance, for my VGM compressor).
Anyway, hope you enjoy! Archive is posted on my site: