It`s a mistake to say “a deal”! The right phrase is “a deal.” The use of an indeterminate article is not only related to the question of whether or not a word begins with a vowel or spelling consonant. It`s related to phonological sound. For example, it is fair to say “a European” and not “a European,” because the sound that starts the word “European” is a consonant. It is therefore not an `agreement`, but an `agreement`. In the language of Khanty, vocal harmony occurs in eastern dialects and affects flexible suffixes and derivation suffixes. The Vakh-Vasyugan dialect has a particularly extensive system of vocal harmony, with seven pairs of front-backs:  A thoughtful discussion of segmental and autosegmental approaches to vocal harmony. In addition to harmony in suffixes, there is a limit of harmony for word trunks, where, in stems of more than one syllable, all vowels must be of the same dimensions of abraction of the lips and the same heights of language. For example, a rod should contain all rounded vowels or rounded vowels, etc. This restriction is further complicated by (i) long, high, lowered vocalizations, and (ii) an epithal vowel [i] that does not harmonize with the usual votes. Most Turkish words have not only vocal harmony for suffixes, but also internally. There are, however, many exceptions.
Moksha, Erzya`s closest relative, has no phonetic vocal harmony, although /a/front and rear has allophones in a distribution similar to Erzya`s vocal harmony. There is some evidence of vocal harmony according to vocal pitch or ATR in the prefix i3/e in the pre-Sargonic Lagash inscriptions (the peculiarities of the model have brought a handful of scholars, Many cases of partial or complete vocal assimilation of certain prefixes and suffixes to an adjacent syllable are reflected in writing in later periods, and there is a noticeable, though not absolute, tendency for disyllabic strains to have the same vocal in both sions.  What appears to be a vocal contraction during the break (o/aa/, `/ia/, `/ua/> a, `ae/> a`, `/ue/> etc.) is also very common. The result was that the back vowels ended after a palate consonant and consonants were palatalized in front of j or an earlier vocal.