Has anyone done this?

...Plus I've never heard any device or algorithm pitchbend any audio material more than two semitones without messing it up in terms of quality...

There are existing DSP boxes that can do pitch shifting very nicely. I had an idea for a vocal harmonizer years ago, but once I found out just what all DSP entailed at the time I abandoned. Now you can buy it from Guitar Center and other music stores.

I think even my $100 Behringer effects unit can do that if I work at it.

Don