The tonal accent (TA) of Somali undergoes many variations that remain understudied and poorly understood. This paper investigates two of the most important of these variations, which both imply the pitch lowering of the TA. The first lowering involves the last TA of a subject NP. Specifically, the high tone of the TA (H*) becomes mid (M) or low (L) and has been analyzed as resulting from the de-accentuation of the word. The other lowering has been described as the general process whereby a H or M tone is realized at the next tone level below (HM, ML), just before a pause. This paper argues that both pitch lowerings result from the interaction between the H* and a L tone associated with a prosodic constituent. In subject case, the L tone is assumed to be a tonal morpheme that is associated with the phonological phrase and delinks the last H* in a subject NP. In a pre-pausal context, the L tone is a boundary tone associated with higher constituents and only has a local lowering effect on the last mora of those constituents.