A polyglot text-to-speech synthesis system which is able to read aloud mixed-lingual text has first of all to derive the correct pronunciation. This is achieved with an accurate morpho-syntactic analyzer that works simultaneously as language detector, followed by a phonological component which performs various phonological transformations. The result of these symbol processing steps is a complete phonological description of the speech to be synthesized. The subsequent processing step, i.e. prosody control, has to generate numerical values for the physical prosodic parameters from this description, a task that is very different from the former ones. This article shows appropriate solutions to both types of tasks, namely a particular rule-based approach for the phonological component and a statistical or machine learning approach to prosody control.