I’ve been listening to the level 3 northern course again for a bit of revision and it has struck me that I have never quite grasped when it is better to use the possessive construction with a verb noun to express the object, and when it is more appropriate to drop the possessive and just use the echoing pronoun. I know Catriona has asked a similar question, and Gareth did answer it, so I understand the grammar here, but that still leaves a question of style.
For example, in one dialogue I hear:
Mae’n fyd mawr ond dydi hynna ddim yn meddwl na fedrwn ni ei newid.
But in another I hear:
Gad i mi daflu fo dros y wal.
Would it make no difference whatsoever if these were:
Mae’n fyd mawr ond dydi hynna ddim yn meddwl na fedrwn ni newid o.
and
Gad i mi ei daflu (fo) dros y wal.
Or do the first versions as actually used in the dialogues sound more natural and euphonious to a Welsh speaker?
Yes I think you are correct in your final question. I think it’s just that some patterns don’t feel right being shortened or overlengthened. Ideas like changing, being born or brought up, etc, sound a bit strange if you try to just use the verb alone as in English. Similarly, over-lengthening simplified patterns into those extended forms can seem strange.
I suppose its something parallel (but not exactly the same) as mixing up the following patterns in English:
I was born and grew up.
You can’t get away with-
I borned and was grew up
Grammatically, my understanding is that it’s always fine to use both the possessive adjective and the pronoun together. Dropping the pronoun is de rigeur in formal writing, but also reasonably common in the spoken language, and considered correct. It’s also quite common to drop the possessive adjective and sometimes the pronoun in the first person singular if word in the middle has a nasal mutation.
Forms where the pronoun is used without the possessive adjective - saying things like bo fi, bo chdi instead of fy mod i, dy fod ti - are frowned upon by some people but also really widespread.
As to what you do actually leave in or take out, I suspect there are a few factors:
If the pronoun is implied by the possessive adjective as is the case for the first and second person, both singular and plural.
Whether the pronoun is implied by a mutation or lack of it in the middle word in the third person.
How obvious the pronoun is from context.
Rhythm, cadence, what other consonants are around and so on.
How quickly the person is speaking and whether they’re being deliberate for effect.
Taking “Mae’n fyd mawr ond dydi hynna ddim yn meddwl na fedrwn ni ei newid” as an example, it might be fine to say that when speaking slowly and deliberately, but at speed, it might sound too similar to “Mae’n fyd mawr, ond dydi hynna ddim yn meddwl na fedrwn ni newid” which obviously has a different meaning. In that case putting the pronoun in would remove the ambiguity.
I hope this helps. I don’t really have an answer, but it’s an interesting topic.