This may be old hat, (and I’m in a rush so not doing a search), but this came up on the SDIY list.
It’s a speech synth using a SID and 6502 assembler on the C64, I figure anything a 6502 at 1/2MHz can do can be done by a PIC at 20…
http://noname.c64.org/csdb/release/viewpic.php?id=48099
Just a thought
Mike