I'm asking specifically about Yod* coalescence when connecting two words together.
Some very (neat) phenomenon in American English is to "fuse" you/r/s when the word ends in t/d/z:
I was thinking about you -> aɪ wəz θɪŋkɪŋ əˈbaʊtʃu
what did you do? -> wʌt| dɪʤu du?
close your eyes -> kloʊʒəɹ aɪz
From my observation, Americans only coalesce some or non of the t+y, d+y and z+y combination, depending on their regional accent and how articulate they want to sound (the more they coalesce, the informal it sounds).
Another observation I have is that across words (I'm not talking about inter word combinations like future, solider and vision), it can only happen when the second word is you/your/yours.
Am I correct? are there any other words which start with y and can be coalesced? or the only "valid" coalescence is when the second word is you/r/s?
I mean, one can't say "but yeah, you're right" as something like "bucheah, you're right" without sounding very awkward.
If anyone wants to answer about different dialect of English (British, Australian,etc.) they are welcome, but the question is about American English, with bias toward Midwestern/West coast/General American accent.
*hey, that's a Hebrew letter!
Best Answer
This coalescence is not so special. It actually seems to be natural and normal at times.
"And now, about yesterday" could be heard as
and the person so speaking not be aware that he never really eaid "yesterday".
It may be that Americans perform this coalescence more than some other English speakers, but it is surely not a new phenomenon.
The Classical Latin word for "yoke" might be used as an example. IUGUM majstro.com in Latin gives a number words in modern languages (the I is equivalent to the English"y").
In Italian wordreference.com we have giogo which sounds much like "jogo" in English spelling.
In English we have "jugular" Wiktionary and "subjugate" from the Latin SUB IUGEM , among others.
Spanish retains the "y" sound: yugo, but French does not: joug. Neither does Portuguese: jogo. Perhaps there was a shift in Vulgar Latin that did not occur in Castilian Spanish. May be there are other explanations.
As to American English, this coalescence might just be normal to the language, and not exceptional. I am an American English speaker. If I say SUB IUGUM as a Latin phrase, formally, the "y" sound will be intact. If I informally say the phrase it might sound like
and I will have committed the coalescence, and not given it a thought.
The pity is we have only recently been able to go beyond good guesses as to how sounds change in language over time. The "y" sound in yesterday may not have been there 1500 years ago. German uses a "hard G" in its current word (gestern) Collinsdictionary.com and some, or all Anglo-Saxon dialects may have had the hard sound instead of "y". It is possible that "y" is not stable in all dialects of English today. I fear it will take thousands of hours of sound recordings to sort this out. This is a very good question.