1. A method comprising: adding a supplemental phoneset to a speech synthesizer front end having an existing phoneset, wherein the supplemental phoneset comprises a cluster feature where initial consonant clusters and a word boundary are marked with diactitics; modifying a unit preselection process by adding costs associated with the supplemental phoneset to a preselection cost that is part of the unit preselection process, to yield a modified unit preselection process; preselecting units from the supplemental phoneset and the existing phoneset based on the modified unit preselection process, to yield preselected units; and generating speech based on the preselected units.