Morning. I’m doing Challenge 14 of Level 1 so I’ve just learnt ‘ddoe’, meaning ‘yesterday’.
I was practicing a bit with my partner, who’s a Welsh speaker, and she told me I’m pronouncing ‘ddoe’ too much like ‘ddoi’ so I’m effectively saying the wrong word.
I can’t hear any significant difference and I don’t know how to correct my pronunciation here, so it’s eroding my confidence a bit and I wince every time I have to say ‘ddoe’ in the challenge.
Does anyone have any tips?
Hmmm, this is a tricky one because in some areas ddoe and ddoi will sound ever so slightly different but in other areas they will sound the same - so whilst your partner isn’t wrong, neither are you!
If this minute (and often non-existent, as @siaronjames correctly pointed out) difference is the kind of thing your partner is picking you up on, then I think you can take that as a (perhaps unintended) compliment to your Welsh! 
By the way…why does ddoi mean? I can’t remember and can’t find it in the dictionary!
It’s a future tense of ‘dod’
If this minute (and often non-existent, as @siaronjames correctly pointed out) difference is the kind of thing your partner is picking you up on, then I think you can take that as a (perhaps unintended) compliment to your Welsh!
True! She was trying to help me get my pronunciation right because she knows I’m a perfectionist, but I just couldn’t pin down the difference between one and the other, even when she was demonstrating. Then (being a perfectionist) I worried about coming out with a nonsensical sentence because I didn’t get the right inflection.
OK, I challenge the grammar buffs to come up with a sentence where, in context, ‘ddoe’ and ‘ddoi’ could possibly be confused! You’ll have been told before, @alan-charlesworth, that Perfect is the Enemy of Good. And personally, I’m aiming at Just Good enough To Be Understood…
Oops, sometimes I have the impression it’s probably a verb but can’t guess it. 
And I don’t know where to find it!
Going back to the original topic, in Datblygu songs I heard ddoe = ddoi (which is one of the reasons why I find spelling a bit complicated to figure out, although still way easier than English or French, of course.
A workaround might be saying…ddo? 
(like Iestyn, in SSiW I seem to remember)
OK, so I’m a few decades away from becoming a buff, but I love a challenge. How about this for:
I remember yesterday when you said “I’ll be going to the shops, will you come with me?”
Here goes -
Dwi’n cofio ddoe pan dwedest di “ai i’r siopa, ddoi di efo fi?”
I’m not feeling so confident now. How did I do?
I think both those could only mean one thing in context. But what do I know?
Well to be fair, a conjugated form of an irregular verb (which is exactly what ‘ddoi’ is) is probably the hardest thing to try and find in most dictionaries!
I still have a dictionary from when I started learning - https://shop.bangor.ac.uk/product-catalogue/ysgol-y-gymraeg-ac-astudiaethau-celtaiddschool-of-welsh-and-celtic-studies/wlpan/geiriadur-gair-i-gall which does actually give you conjugated forms of irregular (and regular) verbs and directs you to the verb itself.
challenge accepted!
“Ddoi” yw gair sy’n drysu fi
“Ddoe” yw gair sy’n drysu fi
But to be honest, that’s about all I can come up with - I’d say in 99.9% of sentences, context would indeed make them very difficult to confuse.
I pronounce ddoe as ddoi when practising although locally it is pronounced ddoe. That is because when I first started learning that is what we were taught and when singing in a choir we have to pronounce the words ‘correctly’.
I would think - if you want to be very correct - that you would pronounce ddoe something like “ddo-eh” and that ddoi would be more like “ddo-ee” … but I could be wrong.
My experience (from 12 years living in a Welsh-speaking area) has been that they’re both pronounced roughly the way “oi” would be in English, but it seems that in Gwynedd there’s a very slight inflection on the “oe” sound which makes it different if you know what you’re looking (listening) for.
That’s quite amusing. The irony of a future tense sounding like yesterday is worth savouring. It’s up there with the French ambiguity of pronunciation of ‘au dessus’ and ‘au desous’ for above and below. Stuff can end up anywhere. 
I had a very similar question - in Challenge 19 I noticed y bêl-droed was pronounced “bell droad” (rhyming with English “road”) rather than “droid” as in “Android”. Similarly, “ddoe” seems to be pronounced like English “though”. I always thought “oe” was “oi” - when people say “Croeso!” it sounds to me like “Croy-so”, not “Crow-so”, so is there a difference between the “oe” in croeso and the oe in ddoe and droed? I’m using the South Walian version of SSiW.
No, only a difference in regional pronounciation - just like you’ll come across ‘pethau’ pronounced as ‘pethe’ in some areas and ‘petha’ in others, for instance.
Even though I’m used to the different pronunciations of ddoe and pêl-droed I remember being quite puzzled once by a speaker who kept mentioning what sounded a bit like “cord” until I twigged 
he was talking about “trees” - coed. It was the strongest variation of that particular sound I’d heard!