Finite state processing of tone systems

Abstract

It is suggested in this paper that two-level morphology theory (Kay, Koskenniemi) can be extended to include morphological tone. This extension treats phonological features as I/O tapes for Finite State Transducers in a parallel sequential incrementation (PSI) architecture; phonological processes (e.g. assimilation) are seen as variants of an elementary unification operation over feature tapes (linear unification phonology, LUP). The phenomena analysed are tone terracing with tone-spreading (horizontal assimilation), downstep, upstep, downdrift, upsweep in two West African languages, Tem (Togo) and Baule (C6te d'Ivoire). It is shown that an FST acccount leads to more insightful definitions of the basic phenomena than other approaches (e.g. phonological rules or metrical systems).