ENVOICE is a concatenative speech synthesis system developed by the SLS group. ENVOICE creates synthetic speech by concatentating segments of speech from a pre-recorded speech corpus. The concatentation of segments can occur at the phrase, word, or sub-word levels. The choice of segments to concatenate is determined by searching the pre-recorded corpus to find the segments best matching a set of concatenation constraints. ENVOICE takes advantage of finite-state transducer (FST) technology to efficiently deliver synthetic speech on-demand.