Tshivenda (Bantu, Guthrie S21) is similar to other Southern Bantu languages in displaying the conjoint / disjoint alternation: The simple present / habitual is expressed either with the prefix /a-/ or with a bare verb stem. While in related languages (e.g. Zulu, Hapert 2016) these two forms are in complementary distribution based on the syntactic environment, in Tshivenda I will show they show an interesting three-way distribution depending on the post-verbal material: The prefix /a-/ is obligatory in some contexts, impossible in others, and optional elsewhere. Strikingly, the same three-way split turns up in the distribution of penultimate lengthening. Penultimate lengthening is a prosodic phenomenon common to many of the Bantu languages which causes the penult of some prosodic unit to be lengthened; this unit is typically taken to be the intonational phrase (Hyman 2009). I will present the results of a production experiment showing that in Tshivenda sentence-internal penult lengthening occurs variably and shows a three-way split: In some syntactic contexts it shows frequent lengthening; in others, infrequent; and in still others, no lengthening at all. The syntactic contexts which condition this distribution are the same as those that condition the conjoint / disjoint alternation. I will present an analysis of the Venda conjoint / disjoint alternation whereby the disjoint prefix appears exactly when the verb is last in an intonational phrase. Based on the distribution of penultimate lengthening, I argue that Tshivenda shows variability in both the prosodic structure itself and in the marking of that structure; the variability in the structure itself accounts for the contexts in which either conjoint or disjoint form is available.