System Of OE Vowels And Their Origin Word Stres

All the Germanic languages of the past and present have common linguistic features; some of these features are shared by other groups in the IE family, others are specifically Germanic.
In ancient IE, prior to the separation of Germanic, there existed two ways of word accentuation: musical pitch and force stress. The position of the stress was free and movable, which means that it could fall on any syllable of the word a root-morpheme, an affix or an ending and could be shifted both in form-building and word-building. In Early PG word stress was still as movable as in ancient IE but in Late PG its position in the word was stabilized.
The stress was now fixed on the first syllable, which was usually the root of the word and sometimes the prefix; the other syllables suffixes and endings were unstressed. The stress could no longer move either in form-building or word-building. Unstressed vowels were weakened and dropped. Stressed vowels underwent some changes: splitting: 1 phoneme split into several allophones which later become separate phonemes: (a:э);merging:separate phonemes become allophones of one phoneme and then disappear and are not distinguished any more as separate phonemes (a:o:э:)In PG there were no diphthongs. There was just a sequence of two separate vowels.Diphthongs appeared in OE: some (usually long diphthongs)as result of merging of two vowels:a+u=ea;e+u=eo.Others(usually short diphthongs)as a result of the influence of the succeeding and preceding consonants (breaking of э, e).
Mutation a change of one vowel to another one under the influence of a vowel in the following syllable. Palatal mutation (or i-Umlaut) happened in the 6th -7th c. and was shared by all Old Germanic Ls, except Gothic.
Palatal mutation fronting and raising of vowels under the influence of [i] and [j] in the following syllable (to approach the articulation of these two sounds).As a result of palatal mutation: [i] and [j] disappeared in the following syllable sometimes leading to the doubling of a consonant in this syllable; new vowels appeared in OE (ie,y) as a result of merging and splitting.(before palatal mutation a,o,э->е;a:->/э:/o/o:->у/у: labialised;eo/eo:->ie/ie:).In OE Vowel System each short vowel had its long variant. The length of vowels served to distinguish words:OEcol(coal) co:l(cool);god(god) go:d(good)