Peculiarities of Middle English spelling
For letters indicating two sounds the rules of reading are as follows.
G and c stand for [®] and [s] before front vowels and for [g] and [k] before back vowels respectively.
Ystands for [j] at the beginning of words, otherwise it is an equivalent of the letteri, as in NE, e.g. ME yet [jet] ‘yet’, knyght [knix't] ‘knight’, also veyne or veine ['veinə] ‘vein’.
The letters thand sindicate voiced sounds between vowels, and voiceless sounds – initially, finally and next to other voiceless consonants: ME worthy ['wurði] ‘worthy’, esy ['e:zi] ‘easy’, thyng [i] ‘thing’, sorwe ['s]rwə] ‘sorrow’. Note that in ME – unlike OE – this rule does not apply to the letter f: it stands for the voiceless [f] while the voiced [v] is shown by vor u; cf. ME feet [fe:t] ‘feet’ and vayn [vein] ‘vain’.
As stated above, o usually stands for [u] next to letters whose shape resembles the shape of the letter u, though sometimes even in the same environment it can indicate [o], cf. ME some ['sumə] ‘some’ and mone ['mo:ne] ‘moon’. To determine the sound value of o one can look up the origin of the sound in OE or the pronunciation of the word in NE: the sound [u] did not change in the transition from OE to ME (the OE for some was sum); in NE it changed to . It follows that the letter o stood for [u] in those ME words which contain  today, otherwise it indicates [o]. Cf., e.g. ME some ['sumə] ‘some’, not [nOt] ‘not’.
The digraphs ouand ow were interchangeable. Their sound value can be determined either by tracing the words to OE prototypesor by taking into account the modern pronunciation. They indicate [u:] in the words which contained [u:] in OE, since the OE [u:] had not changed and which have [au] in NE, e.g. OE hãs > ME hous [hu:s] > NE house. If the modern word has [ou], the corresponding ME word should be pronounced with the same diphthong [ou], e.g. ME snow [snou], NE snow, as ME [ou] has not altered.
Long sounds in ME texts are often shown by double letters or digraphs. The length of the vowel can sometimes be inferred from the nature of the syllable; open syllables often contain long vowels, while closed syllables may contain both short and long vowels. The succeeding consonant groups can also serve as indicators: vowels are long before a sonorant plus a plosive consonant and short before other consonant sequences, eg. ME maken ['ma:kən] ‘make’, lat [la:t] ‘late’, lok [l]k] ‘lock’ bihynden [bi'hi:ndən] ‘behind’, bisetten [bi'settən] ‘beset’.
In reading ME texts there is no need to observe the distinctions of sound length but these distinctions are most important for a proper understanding of ME and Early NE sound changes.
The opening stanzas of the Prologue to the CANTERBURY TALES by G. Chaucer (late 14th c.) are given below with transcription and translation; the word stress is shown as required by the iambic meter of the poem and is therefore marked both in monosyllabic and polysyllabic words.
(1) Whan that Aprille with his shoures soote
[xwan 'at ap'rillə 'wi his 'u:rəs 'so:tə]
(2) The droghte of March hath perced to the roote,
[ə 'druxt of 'mar± ha 'persəd 'to: ə 'ro:tə]
(3) And bathed every veyne in swich licour,
[and 'ba:ðəd 'evri 'vein in 'swi± li'ku:r]
(4) Of which vertu engendred is the flour;
[of 'xwi± ver'tju: en'®endrəd 'is ə 'flu:r]
When April with his sweet showers
The draught of March has pierced to the root,
And bathed every vein in such liquor,
Of which (whose) virtue (power) engendered is theflower.
Changes in the phonetic system in Middle English
The word stress
In OE the stress usually fell on the first syllable of the word, rarely on its second syllable: the prefix or the root of the word could be stressed while the suffixes and endings were unaccented. Word stress in OE was fixed: it never moved in inflection and seldom in derivation.
This way of word accentuation, characteristic of OE, was considerably altered in the succeeding periods. The word accent acquired greater positional freedom and began to play a more important role in word derivation. These changes were connected with the phonetic assimilation of thousands of loan-words adopted during the ME period.
New accentual patterns are found in numerous ME loan-words from French. Probably, when they first entered the English language they retained their original stress – on the ultimate or pen-ultimate syllable. Gradually, as the loan-words were assimilated, the word stress was moved closer to the beginning of the word in line with the English (Germanic) system. In disyllabic words the accent moved to the first syllable, so that the resulting pattern conformed to the pattern of native words, e.g. ME vertu [ver'tju:] became NE virtue ['və:±ə], cf. native English shortly, childish. The shift can be shown as follows: s's>'ss (s stands for "syllable").
In words of three or more syllables the shift of the stress could also be caused by the "rhythmic" tendency, which required a regular alternation of stressed and unstressed syllables. Under the rhythmic tendency, a secondary stress would arise at a distance of one syllable from the original stress. This new stress was either preserved as a secondary stress or else became the only or the principal stress of the word, e.g.
ME recommenden [reko'mendən] > NE recommend [1rekə'mend] – ss’ss > 1ss's;
ME disobeien [diso'beiən] > NE disobey ['diso'bei] – ss'ss > 'ss's;
ME comfortable [komfor'tablə]>NE comfortable ['kmfətəbl] – ss:>'sss.
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. ME accepten ‘accept’, engendren ‘engender’, presenten ‘present’. Cf. NE verbs befall, mistake, forget. Corresponding nouns sometimes, though not always, received the stress on the first syllable: NE 'present n – pre'sent v; 'discord n – dis'cord v. The latter pairs of words show that the role of word accentuation has grown: word stress performs a phonological function as it distinguishes a verb from a noun.
Thus, the entire system of word accentuation has altered. The position of word stress has become relatively free and its phonological application has widened: it can be shifted in word derivation, though it is never moved in building grammatical forms.