The application will be for stuttering aid. The voice of the stutterer will be altered and sent back to his ear.

We will give them to the members of our stuttering association.

I already know the holtek chips the 8950 is not manufactured anymore and the 8970 is difficult to find. Yamaha has a msm6722 for pitch shifting...

What I need is a low price solution. And someone told me that's possible to do with a 8051...

The sound quality doesn't need to be CD-like.