Morphological parsers are typically developed for languages without contrastive tonal systems. Ha, a Bantu language of Western Tanzania, proposes a challenge to these parses with both lexical and grammatical pitch-accent (Harjula 2004) that would, in order to describe the tonal phenomena, seem to require an approach with a separate level for the tones. However, since the Two-Level Morphology (Koskenniemi 1983) has proven successful with another Bantu language, Swahili, it is worth testing its possibilities with the tonally more challenging Bantu languages.
However, the parsing formalism presented here does not always describe the tonal phenomena that are found in the Ha language. With some type of accents the lexical accents can be mapped directly to the surface realisations, but with others the interaction of the accents causes changes on the segmental level, or the morphophonemic changes of the segmental level affect the realisations of the accents. Thus, for proper description of the language, a formalism which would allow the tones or accents to be mapped with the segmental level only after certain rules have applied in the two levels separately, is required.
Koskenniemi, Kimmo, 1983. Two-level morphology: A general computational model for word-form recognition and production. Publications No.11. Department of General Linguistics, University of Helsinki.