I am grateful for responses from PersoLatin and Alfaaz and marrish SaaHibaan. All three have said that the word گفتگو is "guft-u-guu" (PersoLatin has indicated this as "goftogu" which is the modern Iranian Persian pronunciation). If گفتگو is fully vocalised then we are all in agreement that it is written as گُفْتُگُو. I am aware that Persian speakers do not place a -ُ over the گ which as far as I understand is a convention of the Persian written language of modern times, because as far as they are concerned the و alone provides the -uu sound in the said word.
My reason for requesting friends to vocalise گفتگو concerns exclusively the presence or absence of a -ُ over the ت and all three responders have placed the -ُ over the ت. I too do the same. However, in another forum an Urdu poet writes this word with a "sukuun" or "jazm" over the ت, that is to say "guftguu" and I wanted to find out how Persian and Urdu members of the group perceived the pronunciaion of this word.
guftuguu is given in the following dictionaries.
LuGhat Nama - Iranian Persian Dictionary
Sulayman Hayyim - Iranian Persian Dictionary
Kitabistan 20th Century Standard- Pakistani Dictionary
guftguu is given in the following dictionaries
Steingass - Indian (Indo-Persian) Dictionary
Platts - Indian Urdu Dictionary
Urdu LuGhat- Pakistani Urdu Dictionary
Based on this and the additional comment in marrish SaaHib's post, it appears that in modern day Urdu, the common pronunciation is
guftguu which strangely enough is in variance with the views of three persons in this forum from Urdu background! But three people from Urdu background and one from Persian is not large enough a number to draw statistical conclusions!
So, what is the correct pronunciation. Well, based on the perspective of one Persian speaker, three Urdu speakers, two Persian dictionaries and an Urdu dictionary, the word ought to be
guftuguu. If we take into account our Urdu poet from another forum, marrish SaaHib's quote from a well known authority on the Urdu language and three dictionaries (One Indo-Persian and two Urdu), the word is
guftguu. Not much to chose from and the score is almost level and there is no clear discernable difference! I was hoping that
guftuguu would be a clear outright winner. One lives in hope!
Why should it be "guftuguu"? Well, language pronunciations change but theoratically speaking it should be "guftuguu". Why?
Below I am copy/pasting a section from my own post from an earlier thread.
Hindi: व
As you have indicated, the word for "and" in Persian was -u- (equivalent to a pesh). When the Persian language began to be written in the Arabic alphabet which normally showed no short vowels, there was no real problem when a word like "gul" was simply written as "gl". But to indicate -u- for and, the next best thing was to use an Arabic letter which was connected to -u-, namely "waaw".
So, aab-u-havaa was written as آب و ھوا
du (two) as دو
tu (thou) as تو
chu (like) as چو
In all such words the -u- had a "pesh" sound, just like the pesh vowel in "gul". Even today, in Dari, the word for "two" is NOT "do" but, "du" and for "thou", it is "tu" and NOT "tuu" (as we pronounce the Persian تو nor "to" as the Iranians pronounce the تو).This -u- sound over a period of time became a majhuul -o-sound, as in "aab-o-havaa" and the Iranian "to" and "do". (Our Persian "tuu" could be influenced by our Urdu "tuu". Same goes for "do"). So, apart from the Dari "du" and "tu", the-u- sound on the whole has become-o-, just like the izaafat-i-, has become the majhuul -e- in Indo-Persian, Dari and Iranian Persian.
What is all this leading to. It is this representation of the original -u- with the Arabic Waaw, that could be a "polluting" factor in our thinking that the Persian '-u-' is of Arabic origins. It is quite possible that the letter waaw representing the sound -u-in the written documents began to be read as one would read an Arabic "waaw", ie. "wa". This then fluctuated between wa and va.
I don't have any scholarly proof for this. Just think of it as Qurehpor's hunch!!
eskandar SaaHib had this to say.
"I believe your hunch is quite right! In Middle Persian, logograms (huzvarishn) were often used where words were written according to their Aramaic meaning but pronounced according to Middle Persian. For example, shaah (king) was written MLK (Aramaic 'malka', cognate to Arabic ملك 'malik') but read as 'shaah'. (See more examples
here). As far as I know the Persian use of و (or its Aramaic equivalent) began as a logogram for 'u' and continued in New Persian written in the Arabic alphabet, with و primarily representing 'u' (later 'o') and then later it began to be read as 'wa' (later 'va') as well."
Finally, here is a chunk from fdb SaaHib's post.
"There are two words for “and” in Persian, which, confusingly, are both written as و.
There is the inherited Persian word
u, from Middle Persian
ud, from Old Persian
uta. This is purely Indo-European. In modern Persian this is normally only used if the two words connected by it are in close junction.
Then there is the Arabic word
wa. This is pure Semitic.
It is true that in Middle Persian (Pahlavi) the conjunction
ud is written with the Aramaeogram W. Aramaic
w-, wa- is indeed cognate with Arabic
wa, but this has no bearing on New Persian or Hindi/Urdu. The Muslims in Persia and India could not read Pahlavi and were not affected by the vagrancies of Pahlavi spelling."