Empirical Analysis of Tonal Downstep Phenomena in the Oyo and Ekiti Dialects of Yoruba

Tonal downstep is a phonological phenomenon with significant implications for how semantic distinctions are maintained in tone languages, and its comparative analysis across dialects provides important evidence for theories of tonal grammar. This study conducts an empirical analysis of tonal downstep phenomena in the Oyo and Ekiti dialects of Yoruba, two geographically and historically related but phonologically distinct varieties. Using instrumental phonetic methods, including acoustic analysis of pitch contours extracted from recordings made with 60 native speakers across both dialect groups in Oyo and Ekiti States, the study compares the conditioning environments, pitch scaling properties, and surface realisations of downstep in natural speech. The theoretical framework draws on autosegmental phonology and the floating tone hypothesis. Existing literature on Yoruba tonal downstep has primarily used the Oyo dialect as its analytical base, creating a gap in comparative dialect phonology for Ekiti. This study addresses that empirical gap with cross-dialectal acoustic data. The research investigates whether downstep triggers and spreading mechanisms are identical across both dialects or whether Ekiti presents phonological innovations attributable to contact with neighbouring Edo and Igbo languages. Findings are expected to reveal shared downstep mechanisms with systematic differences in the degree and conditioning of downstep at phrase boundaries. Recommendations will address the revision of Yoruba phonological descriptions to account for dialect variation in downstep and related tonal phenomena. Keywords: tonal downstep, Oyo dialect, Ekiti dialect, Yoruba phonology, acoustic phonetics.