<Li> / æ / and / ɑ / merged to a single central vowel / a / . </Li> <Li> / æː / and / ɑː / raised to / ɛː / and / ɔː /, respectively . </Li> <Li> The diphthongs / eo̯ / / eːo̯ / simplified to new front - round vowels / ø / and / øː /, respectively . Everywhere except in the southwest, these vowels quickly unrounded to become / e / and / eː /, respectively; in the southwest, it took 200 or 300 years for this process to take place, and in the meantime the sounds were spelled ⟨ o ⟩ in texts from the southwest . </Li> <Li> The front - rounded vowels / y / and / yː / unrounded to / i / and / iː /, respectively, everywhere but in the southwest (former West Saxon area) and southeast (former Kentish area). <Ul> <Li> In the southwest, these front - rounded vowels remained, and were spelled ⟨ u ⟩ . </Li> <Li> In the southeast, the vowels had already been unrounded to / e / and / eː /, respectively, in Old English times, and remained as such in Middle English . </Li> </Ul> </Li>

What change did vowels in open syllables undergo during the middle english period