1. A method of synthesizing speech from text, the method comprising: determining a sequence of phonetic components from the text; determining a sequence of target phonetic elements from the determined sequence of phonetic components; determining a sequence of target event types from the sequence of target phonetic components, wherein a target event type in the sequence of target event types represents a plurality of intonation realizations; and selecting a plurality of speech units from a set of stored speech unit candidates to form a sequence of selected speech units, wherein a first speech unit in the sequence of selected speech units is selected using a cost function comprising a unit cost determined with respect to the target phonetic element corresponding to the first speech unit, a concatenation cost determined with respect to at least one speech unit adjacent to the first speech unit, and an event type cost determined with respect to a target event type corresponding to the first speech unit.