I presume swyddogol means official, am I right?
Correct. Swydd (noun) job/office. Swyddog (noun) officer/official [person]. Swyddogol (adjective) - official
This is one of favourite songs … ever @RichardBuck. I bought the CD Tincian in a shop in Pwllheli (Llyfrau Llen Llyn, dw i’n meddwl) a few years ago and the booklet which comes with it explains what it is about, but it doesn’t give the actual words sung. The most they give is 'Tiws wyt ti fel Lliwia (pretty you are like colours - chorus), and Cesail means armpit - a poetic, comforting word in Welsh similar to bosom in English.
Yeah, I got that, and a few other bits - Caru chdi mwy na fi, A dwi’n gweld yn dy lygad di bo’ ti’n gwybod pwy something something (wyf i?), Gorfod cyffuriau, Fedra i’m gweiddi, Wnes i’m sgrechian - that’s all out of sequence but it’s what I can remember off the top of my head.
ETA Woops: gwrthod cyffuriau, of course.
Three songs from an acoustic session Gruff Rhys did for BBC Alba a couple of years ago, that were recently uploaded to the excellent Ffarout youtube channel.
There are some nice videos on the internet of organ music from various Welsh Chapels. This might get you started. You could also search on something like: “organ/choir [Pontardawe or any Welsh Town or City]”, or search for Welsh Male Voice Choir. Just say if I can help further.
Many thanks!
Actually one thing which I have been wondering for a while: do you (or anyone) know why we hear so many male voice choirs in Wales? Women do sing in Welsh choirs sometimes too, right? 
Yes there are some great Women’s and mixed choirs. @Iestyn & Cat will be the experts on this, but my understanding is that choir singing (and also playing in brass bands) grew up with the workers of mining and other heavy industries.
This is Steve Eaves one of my favourite Welsh singers and I love this song. “Nos da Mam”
Helpfully anything posted on YouTube by “DistantDreamer93” has the lyrics in both Cymraeg and Saesneg.
Really enjoyed these, thank you. 
So young and very talented.
Felly ifanc a dalentog iawn?? 
Great videos, thank you 
I hope it’s not an unwelcome correction – I’m taking the question marks and the emoji to suggest you’re checking – felly is ‘so’ as in ‘therefore’. I think you probably want mor, which is ‘so’ as in ‘this much’. Mor ifanc is probably what’s meant.
Thanks very much for the corrections. I always welcome them, as without them we cannot learn! Diolch yn fawr.
You’re welcome. Glad you liked them.
Thanks for the video its amazing.