Considering previous studies on some varieties of Iranian languages, it has implicitly concluded that Compensatory Lengthening (CL) has a double effect in some language varieties. CL refers to the process through which, in response to the omission of one moraic segment, a segment is lengthened to conserve the moraic structure of the syllable. Previous studies have proposed that, based on the type of the target vowel, CL may compensate for the lost mora by either vowel lengthening or by its replacement by the long vowel [ɑ]. In the present study, the cause of this qualitative change in this context has been investigated. Analyzing the trigger consonants, it was indicated that all of them can be classified within the [pharyngeal] natural class according to their shared [RTR] feature. Thorough the pharyngealization harmony process, these consonants spread their distinctive [RTR] feature to their adjacent vowel, which leads to a more back and lower place of articulation which is similar to that of [ɑ]. Due to the similar contexts for the application of the mentioned rules, investigating their interaction indicated that, firstly, through the pharyngealization harmony, the syllable nucleus will be changed into a bimoraic vowel. As [pharyngealized] consonants are subject to deletion in the coda, their deletion leads to a stray mora. However, the context for the lengthening of the vowel has been removed. More clearly, prior to the coda deletion, the short vowel has been changed into a bimoraic one, to which the stray mora cannot be linked.
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