1. A method comprising: when a user is determined to be new, changing a front-end which converts text into linguistic tokens and tags the linguistic tokens with a prosody, a pronunciation, a speech act, and an emotion of the text, to yield a user-specific front-end; in response to a user request from the user to generate a custom text-to-speech voice for a vehicle, the custom text-to-speech voice being associated with a domain, automatically: collecting, via a processor, text data associated with the domain from a pre-existing text data source, to yield collected text data; selecting, based on the user specific front end, synthesis speech units specific to the domain from a pre-existing inventory of synthesis speech units using the collected text data; caching, via the processor, the synthesis speech units specific to the domain as an in-domain inventory of synthesis speech units; and generating, via the processor, the custom text-to-speech voice for a specific task in the domain utilizing the in-domain inventory of synthesis speech units.