Jeff Birt takes a look at digitised speech on the C64 in this first of a series:
Skip to the 20min mark for a bit on Forrest S. Mozer, a physicist who figured out - and patented - ideas for low bitrate speech. Links in the video description, including
- Electronic Speech Systems aka ESS, Mozer’s company
- Mozer compression (" He first licensed the technology to TeleSensory Systems for use in calculators for the blind and then to National Semiconductor for use in the DigiTalker chip. In 1984, he co-founded Electronic Speech Systems (ESS), and the codec ended up playing speech in Commodore 64 games such as Impossible Mission and Ghostbusters .")
- Video Interview with Forrest S. Mozer (transcript on YouTube)
Here’s the calculator mentioned (it’s for the vision-impaired):
A bit of reverse-engineering of the TI chip inside.