Eliza and Blockhead
Eliza was the first psychologist program in the world, and in fact, the first program that allowed a human to converse with a computer. It used Artificial Intelligence (AI) in order to try and imitate a real human psychologist. Joseph Weisenbaum at MIT was the head of that project in 1967. It used an algorithm called CBR, or case based reasoning.
Extremely better, ECC-Eliza is actually a completely rewritten version of Eliza. The source has been rewritten from scratch in modern Pascal and Assembly (combined). A totally new data file that contains all the language information was made and is about 80 times larger than data files of all other Eliza versions.
Let Blockhead be some person speaking with Eliza. The following conversation is used to produce sound. A voice reading the conversation between Blockhead and Eliza is recorded and altered by changing some parameters of the the resulting soundfile.