Verbal performances--ranging from song and recitation of poems to comedy acts and news broadcasts--are rich sites of linguistic variation with great popular appeal. These performances not only reflect language variation, but also drive it, through establishing new registers marked by distinct combinations of linguistic and performative cues. Such cues may include grammatical and lexical elements of a performance, speech style, and meter or form. Combinations of cues become familiar to listeners, and serve to key specific performative registers. Successful verbal performances drive variation in speaker repertoires as speakers absorb new combinations of cues and imitate, reference, or evoke the ambiance of verbal performance in both daily speech and in performative settings. The creative nature of performance leads to the consistent blurring of previously held notions of genre and associated dialect use and complicates both types of categorization. I suggest that comparative study of language use from within a set of contrasting performances can reveal the depth of language variation in performed genres, and its associated performative variation. The effect of verbal performances on speaker repertoires can also be explored through analysis of discourse on performers and their performances, and by following successive performances that share stylistic features or similar combinations of linguistic and performative cues. This paper focuses on dialect and variety in performed poetry, taking as its case study the poetic texts of Umm Kulthum's songs and her performances of these texts. Umm Kulthum’s songs contain the voices of dozens of Egyptian and Arab poets and span diverse poetic and musical forms. In fact, we can consider the lyrics of her songs some of the best known poems among Arabic speakers of all generations, widely understood and memorized. Through analysis of the linguistic and performative cues that mark the range of Umm Kulthum's performances, I suggest that these performances not only reflect the multiglossic Arabic reality but also drive language variation that reaches speaker repertoires.