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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 Quadras of 1993. It was made a standard system component in System 7.1.2, and has since been shipped on all PowerPC and even some 68K Macintoshes.
Speech synthesis 
Apple's text-to-speech uses diphones. Compared to other methods of synthesizing speech, it is not very resource-intensive, but there is a limit to how natural the synthesis can get. See the speech synthesis article for details. 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.
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 synthesiser can be controlled explicitly using a special phoneme alphabet.
Original MacInTalk 
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. 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.
MacInTalk 2 
Eventually, Apple released a supported speech synthesis system, called MacInTalk 2. It supports any Macintosh running System Software 6.0.7 or later. It remained the recommended version for slower machines even after the release of MacInTalk 3 and Pro.
MacInTalk 3, Pro 
MacinTalk 3 introduced a great variety of voices. Apart from the standard adult voices "Ralph", "Fred" and "Kathy", and children's voices like "Princess" and "Junior", various novelty voices were included, including "Whisper", "Zarvox" (a robot voice with melodic background sounds, with a similar voice called "Trinoids" also included), "Cellos" (a voice that sung its text to an Edvard Grieg tune, with similarly-singing voices like "Good News", "Bad News", "Pipe Organ"), "Albert" (a hoarse-sounding voice), "Bells", "Boing", "Bubbles", and others.
Each of these voices came with its own example text, that would be spoken when one hit the "Test" button in the Speech control panel. Some would just say their name, language and the version of MacinTalk they were introduced with. Others would say funny things, like "I sure like being inside this fancy computer", "I have a frog in my throat... No, I mean a real frog!", or "The light you see at the end of the tunnel is the headlamp of a fast approaching train". These voices as well as their test texts are still in Mac OS X today.
With the increase in computer power that the CPUs in AV Macs and PowerPC based Macintoshes provided, Apple could afford to increase the quality of the synthesis. MacInTalk 3 required a 33 MHz 68030 processor and MacInTalk Pro required a 68040 or better and at least 1 MB of RAM. Each synthesizer supported a different set of voices.
Text-to-speech in Mac OS X 
Text-to-speech has been a part of every Mac OS X version. The Victoria voice was enhanced significantly in Mac OS X v10.3, and added as Vicki (Victoria was not removed). Its size was almost 20 times greater, because of the higher-quality diphone samples used.
Speech recognition 
Apple hired many speech recognition researchers in 1990. After about a year, they demonstrated a technology codenamed Casper. It was released as part of the PlainTalk package in 1993. Although available for all PowerPC Macintoshes and AV 68k machines (it was one of the few applications that made use of the DSP in the Centris 660AV and Quadra 840AV), it was not part of the default system install prior to Mac OS X. The user had to do a custom installation of the OS to get speech recognition capabilities.
Apple's speech recognition is voice-command oriented, i.e. not intended for dictation. It can be configured to listen for commands when a hot key is pressed, after being addressed with an activation phrase such as "Computer", or "Macintosh", or without prompt. A graphical status monitor, often in the form of an animated character, provides visual and textual feedback about listening status, available commands and actions taken. It can also communicate back with the user using speech synthesis.
Early versions of the speech recognition provided full access to the menus. This support was later removed, since it required too many resources and made recognition less reliable, only to be re-added in Mac OS X 10.3 as a "universal access technology" called spoken user interface.
The user can launch items located in a special folder, called "Speakable Items", simply by speaking their name (while the system is in listening mode). Apple shipped a number of AppleScripts in this folder, but aliases, documents and folders can be opened in the same way.
Additional functionality is provided by individual applications. An application programming interface lets programs define and modify an available vocabulary. For example, the Finder provides a vocabulary for manipulating files and windows.
In popular culture 
In music 
The MacinTalk speech synthesis can be heard in a few songs:
- "Repeating Yesterday" from As I Lay Dying's Shadows Are Security album used MacInTalk in the intro.
- "Satisfaction" by Benny Benassi, as well as other songs by him
- "Toby's Mac" by tobyMac
- Radiohead's song "Fitter Happier" from the OK Computer album (and featured in the background of "Paranoid Android" from the same album)
- Fall Out Boy used MacInTalk at the beginning of "Grand Theft Autumn/Where Is Your Boy" (Millennium Version) and at the end of the last track and bonus tracks on their Infinity on High album
- The French band Air uses several Macintosh voices in their track "How Does it Make You Feel"
- "Yoshimi Battles the Pink Robots, Pt. 1" by The Flaming Lips features the "Zarvox" voice
- Many Aphex Twin tracks including "Funny Little Man" and "Cow Cud Is a Twin" also feature PlainTalk
- The song "John Orr the Arsonist" by And Then There Were None features a short monologue using this voice.
- "The Vic-E Interpretation - Interlude" from TLC's album FanMail features "Victoria" comparing and contrasting club culture in the USA and Japan.
- "Intro" from OutKast's Stankonia album features the "Bells" voice
- The song "Pomme-C" by French singer Calogero on the album Pomme-C features a short monologue at the very beginning using the voice "Vicki"
- "DWYL" by Phil Joel
- The song "Man That You Fear" by Marilyn Manson ends with the MacInTalk voices repeating, "When all of your wishes are granted, many of your dreams will be destroyed". MacInTalk voices are used again in the music video and live performances of "Antichrist Superstar". The MacInTalk voices repeat "You might as well kill yourself — you're already dead" at the end of the song.
- Most of Mr Oizo's Transsexual EP and Lambs Anger album contains MacInTalk voices
- Korea Idol T-ara's song "Bo Peep Bo Peep" from the Absolute First Album introduction part 'Don't lose your temper so quickly'
- The El-P song "Stepfather Factory", from the 2002 album Fantastic Damage, ends with MacInTalk voices repeating, "Why are you making me hurt you? I love you".
- EBM band Apoptygma Bezerk used MacInTalk Kathy's voice in "Kathy's Song (Come Lie Next To Me)". The VNV Nation Remix also uses the "Victoria" voice.
- In EDM producer Skrillex's track titled "I Wish You All The Luck Of The World", the MacInTalk voice "Alex" can be heard repeating "David, I wish you all the luck in the world" several times in various pitches. A heavily edited sample of this phrase later made up the main melodic hook of his later track "With You Friends".
- Rob & Goldie's 1997 track "The Shadow (The Process Mix by Rick Smith for Underworld)" makes extensive use of the "Victoria" voice, reading a dictionary definition of "shadow" and a poem from the book Process: A Tomato Project.
- Jean-Michel Jarre's album "Métamorphoses" from 2000 uses MacInTalk to generate lyrics on the track "Love, Love, Love".
In film 
A combination of the "Ralph" and "Zarvox" voices serve as the voice of the computerized autopilot, AUTO, in the 2008 Disney-Pixar film WALL-E. "MacInTalk" is credited as the voice of Auto in the film's end credits.
In television 
MacinTalk was used to perform the part of the wheelchair-using motor neurone disease patient with a voice synthesizer in the animated Family Guy episode "Ready, Willing and Disabled", who would later appear again in "Brian the Bachelor" and "Brian Goes Back to College". It was furthermore used in "Peterotica", when Stewie plays with "the speech function on his Macintosh", Using Talking Moose software, Stewie gets his laptop to say "Stewie is cool." and also in "April in Quahog" where MacinTalk Fred voices Stephen Hawking. It was also used to introduce episodes on the anime Serial Experiments Lain. In the Transformers Animated episodes "TransWarped", "Decepticon Air" and "This is Why I Hate Machines", the Autobot Perceptor's voice was performed via MacinTalk speech generation, using the "Fred" voice. It was also used in the short-lived cartoon Whatever Happened to... Robot Jones? as the voice of Robot Jones' father, Dad Unit, and Robot in the first season. It was also used as the voice for the Red vs. Blue character, the lying A.I Gary/Gamma. "Junior" was voicing Robot Jones in the 2000 episode of The Cartoon Cartoon Show, "Whatever Happened to... Robot Jones?". The Mac OS X novelty voice, "Boing", was used for the Robot face (SSF/Splaat) for Klasky Csupo.
In video games 
- MacinTalk was used in the game No More Heroes. Before each boss fight, the "Whisper" voice would announce the current boss's name.
- The video game Grand Theft Auto IV uses "Vicki" as the voice of the DJ of the in-game radio station "The Journey".
- The 2009 video game Machinarium features several Macintalk voices in its ambient music.
- The 3DO version of Star Control 2 used "Bruce" as the voice of the Slylandro Probe. The game credits the voice of the Probe as 840AV. "Agnes" was also used as the voice of the Captain's ship's computer, heard on the first encounter with the Orz race.
- The 1996 video game Safecracker utilizes "Victoria" in two of the advanced safes.
- The Japanese version of Sonic CD uses MacInTalk voices in the background music of Metallic Madness' Bad Future stages.
Apple produced a microphone called "Apple PlainTalk Microphone". It was introduced alongside the AV-enabled Quadras in 1993 but was also sold separately. It had a longer connector, and the tip was used to provide it with extra power. It was designed to be positioned on top of the screen and to be sensitive to sound from the front.
- "Marilyn Manson - Antichrist Superstar Official Music Video". Antichrist Superstar Official Music Video (in English). NME.com. Retrieved 15 August 2011.
- Steve "Capone" Prokopy (2008-06-24). "Andrew Stanton Gives Up the Goods on WALL-E and JOHN CARTER to Capone!". Ain't It Cool News. Retrieved 2008-11-22.