Theory of phonetics

[Fq] The nucleus is pronounced with the bulk of the tongue in the front part of the mouth. The front is mid-way between the position for [e] and [x]. The lips are spread or neutral. [F] is front mid-broad unrounded. While pronouncing the glide the bulk of the tongue moves towards the position for [q].
[F] is more open than either the vowel [e] or Russian [э] before a non-palatalized consonant (“этом”). Don’t replace [Fq] by [F] or [e]. Pronounce a weak Russian [A] after the nucleus. For example, as it is in the word: в конце аллеи. Don’t replace [Fq] by [e].
[Vq] The nucleus is pronounced with the bulk of the tongue in the back part of the mouth, but slightly advanced. The back of the tongue is raised as high as for [V]. [V] is back-advanced high-broad slightly rounded. While pronouncing the glide the tongue moves down to the position of [q].	Don’t replace [Vq] by [V] or[u:] . Don’t omit the glide [q]. [Vq] resembles the sounds in this position: пишу опять.

III. Modifications of Vowels in Connected Speech.
The modifications of vowels in a speech chain can be quantitative, qualitative or
both. These changes of vowels are determined by a number of factors such as the position of the vowel, in the word, accentual structure, tempo of speech, rhythm, etc.
The decrease of the vowel quantity (the shortening of the vowel length) is known as a quantitative modification of vowels, which may be illustrated as follows:

1. 
   The shortening of the vowel length occurs in an unstressed position. In this case reduction affects both the length of the unstressed vowels and their quality.
   

For example, Is it → on or ١in the table? [Pn]
But: This →lamp is on the ١table in the room. [qn]
Is →he or ١she to blame? – [hi:].
But: In the ر morning he a'rrived and 'solved all his١problems. [hI]

2. 
   The length of a vowel depends on its positioning a word. It varies in different phonetic environments. For example, knee – need – neat. The vowel [i:] is the longest in the final position, it is shorter before the lenis voiced consonant [d], and it is the shortest before the fortis voiceless consonant [t].