The 4 project enables the building of speech synthesis systems automatically from data with little or no expert supervision, thus creating speech synthesisers for new languages or domains in a quick, easy and pain-free way. Whilst substantial effort has been invested over the years into developing novel and progressively more natural sounding speech synthesis techniques, there has always been a high entry barrier to building a speech synthesis system in a new language, because conventional methods require expensive linguistic resources, detailed expert knowledge, and a high degree of skill in system `tuning'. The result is that only a very few of the world's languages have speech synthesis systems. For those less widely-spoken languages that do have a system available, the quality of the synthetic speech is not very good, because of the lack of resources available and the lack of skills to `tune' the system. The main objectives of 4 are to address this imbalance by providing Open Source tools to: enable the creation of a voice for any domain in any language, provide an end-to-end framework in which these voices can be automatically built and improved, produce natural and expressive speech synthesis, provide feedback-driven learning to improve systems.