Unaltered morphemes as phonological triggers and targets in Rutooro

Rutooro, a Bantu language spoken in western Uganda, exhibits two processes common to Bantu languages: Mid Vowel Harmony (MVH), by which a high vowel is lowered to mid if it follows a mid root vowel, and Consonant Mutation (CM), by which a high front vowel of certain morphemes trigger a change in the immediately preceding consonant. In forms where both rules could potentially apply, CM applies, but MVH does not, even though its structural description is met. Ultimately, it is shown that MVH is blocked when an alveolar fricative intervenes between the trigger and the target. The most anomalous forms are those that contain the short causative /-i/ and the Perfective suffix /-ir/. In some forms CM would be expected to apply, but does not, and in other forms MVH is expected to be blocked, but is not. The key to the analysis lies in the fact that CM is not a purely phonological process, but rather is only triggered by a small set of specific morphemes. The surface anomalies in the perfect forms can all be accounted for if one formalizes the relevant processes as only being triggered (or blocked) by unaltered [-ir].