1. The comparative-historical method in linguistics

18 ME Word Stress. Vowels in Middle English
In OE stress usually fell on the first syllable of the word, rarely on its second syllable. Word stress in OE was fixed: it never moved in inflection and seldom in derivation. These changes were connected with the phonetic assimilation of thousands of loan-words adopted during the ME period. Gradually, as the loan-words were assimilated, the word stress was moved closer to the beginning of the word. It is known as the “recessive” tendency, e.g. vertu [ver´tju:] became NE virtue [və:t∫ə]. In words of three or more syllables the shift of the stress could be caused by the recessive tendency and also by the “rhythmic” tendency. Under it, a secondary stress would arise at a distance of one syllable from the original stress. Sometimes the shifting of the word stress should be attributed not only to the phonetic tendencies but also to certain morphological factors. Thus stress was not shifted to the prefixes of many verbs borrowed or built in Late ME and in Early NE, which accords with the OE rule: to keep verb prefixes unstressed, e.g. present.
Vowels in Middle English were, overall, similar to those of Old English, except for the loss of OE y and æ so that y was unrounded to i and æ raised toward [] or lowered toward [a].
-addition of new phonemic sound (mid central vowel), represented in linguistics by the symbol called schwa:
, the schwa sound occurs in unstressed syllables and its appearance is related to the ultimate loss of most inflections
Some examples:
day [dai]
cause [kaus]
hous [hus]
-loss of unstressed vowels: unstressed final -e was gradually dropped, though it was probably often pronounced; -e of inflectional endings also being lost, even when followed by consonant (as in -es, eth, ed) (e.g. breathe/breathed), exceptions: wishes, wanted; loss of -e in adverbs made them identical to adjective, hence ambiguity of plain adverbs e.g. hard, fast; final -e in French loanwords not lost because of French final stress, hence cité > "city," pureté > "purity"
French loanwords added new diphthongs, e.g. OF point, noyse > ME point, noise
-vowel length:
phonemic vowel length of OE retained in ME (but lost in Modern English)
short vowels tended to lengthen before certain consonant clusters OE climban, feld > ME climbe, feld ("climb," "field")
lengthening of short vowels in open syllables (syllables ending in a vowel), OE gatu, hopa > ME gate, hope
shortening of long vowels in stressed closed syllables, OE softe, godsibb, sceaphirde > ME softe, godsib ("soft," "gossip,"); exceptions (before -st): OE crist > ME Christ ("Christ")
in a long word (if two or more unstressed syllables followed the stressed one), the vowel of the stressed syllable was shortened (Christ/Christmas [ME Christesmesse],
-some remnants of distinctions caused by lengthening or shortening in open and closed syllables: five/fifteen, wise/wisdom; in weak verbs, the dental ending closed syllables: hide/hid, keep/kept, sleep/slept, hear/heard