The SP0256-AL2 produces all 59 phonemes of the English language plus 5 pauses of different lengths. Each of the phonemes are individually addressable which makes the SP0256 capable of saying anything which can be said in the English language. This is the easiest approach to univeral speech synthesis and the speech quality is that of a good robot voice. Search the net and you will find loads of reference to the use of this chip in robots, with masses of circuit ideas and chip specification.
Chuck, the 76477 can only do some mild sound effects, it wasnt capable of speech unless you got cute in switching which you can do with most any volume port. Reference the 1 bit speech synthesizer on te Apple 2 called SAM: Software Activated Mouth....
"My biggest dream in life? Building black plywood Habitrails"