1. A method comprising: adding a supplemental phoneset to a speech synthesizer front end having an existing phoneset wherein the supplemental phoneset is a cluster feature where initial consonant clusters are marked with diacritics; modifying a unit selection process by adding costs associated with the supplemental phoneset to a selection cost that is part of the unit selection process, to yield a modified unit selection process; and generating speech using units from the supplemental phoneset and the existing phoneset, wherein the units are selected by the modified unit selection process.