Hello Jeff,

The SC-4X from Sensory is a chip for speech recognition and
synthesis. This component is in fact a microcontroler with
speech functions.

http://www.sensoryinc.com/html/products/rsc4x.html

You could use phonemes or diphonemes for speech synthesis.
They are small elements of speech. You can create what you
want with small chunks (like a LEGO or a MECCANO) for sound
synthesis : speech or music.

The discontinued Philips MEA8000 used a white noise generator and
a configurable filter for substractive synthesis.

A simpler solution is use of a DAC or PWM with a low pass filter.
Tables of phonemes or diphonemes does certainly exist somewhere
on the WEB. Search in universities sites.

Best regards,

Jean MASSON