PlainTalk

PlainTalk is the collective name for several speech synthesis (MacInTalk) and speech recognition technologies developed by Apple Inc.

In 1990, Apple invested a lot of work and money in speech recognition technology, hiring many researchers in the field. The result was "PlainTalk", released with the AV models in the Macintosh Quadra series from 1993. It was made a standard system component in System 7.1.2, and has since been shipped on all PowerPC and some other 68K Macintoshes.

Apple's text-to-speech uses diphones. Compared to other methods of synthesizing speech, it is not very resource-intensive, but limits how natural the speech synthesis can be. American English and Spanish versions have been available, but since the advent of Mac OS X, Apple has shipped only American English voices, relying on third-party suppliers such as Acapela Group to supply voices for other languages (in OS X 10.7, Apple licensed a lot of third-party voices and made them available for download within the Speech control panel).

An application programming interface known as the Speech Manager enables third-party developers to use speech synthesis in their applications. There are various control sequences that can be used to fine-tune the intonation and rhythm. The volume, pitch and rate of the speech can be configured as well.

Input to the synthesizer can be controlled explicitly using a special phoneme alphabet.

The initial Macintosh text-to-speech engine, MacinTalk (named by Denise Chandler), was used by Apple in the 1984 introduction of the Macintosh in which the computer announced itself to the world (and poked fun at the weight of an IBM computer). While it was incorporated into the Macintosh's operating system, it was not officially supported by Apple (though programming information was made available through an Apple Technical Note). MacinTalk was developed by Joseph Katz and Mark Barton who later founded SoftVoice, Inc. which currently markets TTS engines for Windows, Linux and embedded platforms.

...
Wikipedia