Is it possible he meant to produce a synthesised speech system? Personally, I find the ISD chips to be (bluntly) pieces of *crap*. Yes, they work. Yes you can use address them, but this is a pain in the ass.

Back in the early 1980s there were a plethora of speech synthesis solutions in DIP style. The most famous combo was the CTS256-2AL and SPO256-2AL chips. Together, these chips could simply read an RS-232 text input and say the text. I used this technique on a basic stamp based robot I made a couple years ago. One command in the robot could make it speak. Something like serout 9600,n,8,1 "Text to speak". I've not used the bs2 in years now, but something similar could be done with the 8051. Unfortunatly the chip is hard to find now and virtually no documentation for it exists.

Other solutions are the "speak and spell" speech chip, and the chip used for the TI99a speech boxes. I'm sure you could find either of these items on ebay for $10.