I made a big breakthrough a few days ago when I found a site that had most of Gorky's Zygotic Mynci's song lyrics......
http://www.gorkys.freeserve.co.uk/gorkys/disco/albums/albums.htm
..... and today I found a more comprehensive listing of a whole lot of Welsh bands and their lyrics, often including English translations too ....
http://welshmusic-cerddoriaethcymraeg.tumblr.com/
As an example, here's the words to "Swigod" ( el Parisa & Clinigol) which were on there ....
Swigod - Clinigol & El Parisa
Can/Song: Swigod
Canwr/Singer: Clinigol & El Parisa
Album: Swigod
Geiriau:
Ni dan y sêr,
ai a ti i'r hudol le tan y wawr,
chwarae'r nos a bore, dim ond i ni,
byth yn blino, byth yn colli egni - ffwrdd a ni!
Paid trio gwadu beth sydd o flaen dy lygaid,
dyma’n amser ni nawr.
Paid trio gwadu y wen sydd yn dy lygaid,
meddwi ar y swigod ti a fi.
O chwytha dy swigod arna i, (x 3)
mae fel yfed swigod.
Aur yw popeth melyn,
cymryd drosodd yeah yn mynd syth i’m mhen.
Dyma’m nerth a’m gwendid,
sdim eira gwyn pan mae'r swigod yn gogleisio fel hyn.
So beth os mae'n bwriad ni yw i ddadeni?
Dyma'n amser ni nawr.
So beth os nag y nhw'n rhannu yr eironi?
Meddwi ar y swigod ti a fi.
O chwytha dy swigod arna i (x 3)
Mae fel yfed swigod.
and here's the actual song ..... once you get all the words, and get beyond the poppy bluster, it's a fine love song in itself ...