I disagree that vowel harmony is the place to discuss i-mutation in Welsh. I see no reason why this article, or umlaut and a-mutation for that matter, should be restricted to Germanic. I think this article should be about any fronting/raising process triggered by a following high front vocoid, regardless of what language it's attested in. Likewise a-mutation shouldn't be restricted to Germanic but should include lowering caused by a following /a/ in other languages as well (again an example from Welsh: gwyn 'white (masc.)' < *windos vs. gwen 'white (fem.)' < *windā). Umlaut should mostly be about the written sign, with an indication that it also the name for processes like i-mutation and a-mutation. Vowel harmony should be about the left-to-right processes typical of Uralic and Altaic languages. That's what I think. /comhrá