Techniques for converting text to speech having emotional content. In an aspect, an emotionally neutral acoustic trajectory is predicted for a script using a neutral model, and an emotion-specific acoustic trajectory adjustment is independently predicted using an emotion-specific model. The neutral trajectory and emotion-specific adjustments are combined to generate a transformed speech output having emotional content. In another aspect, state parameters of a statistical parametric model for neutral voice are transformed by emotion-specific factors that vary across contexts and states. The emotion-dependent adjustment factors may be clustered and stored using an emotion-specific decision tree or other clustering scheme distinct from a decision tree used for the neutral voice model.