FWIW, some of my favorite Welsh trad. music performers and recordings:
Gorau Gwerin series of collections ("Best of Welsh folk")
The above all available from Sain.
Also, a good recent recording from Saydisc (CD-SDL 406):
Traditional songs of Wales (Caneuon traddodiadol Cymru)
performed by Siwsann George.
Sain, of course, also has many recordings of fine choral singing.
I think there was a request for The Ash Grove. In case no one else
responded, the following is one of many verses and versions:
Ym mhalas llwyn onn gynt, fe drigai pen defig,
Efe oedd ysgweiar ac arglwydd y wlad;
Ac iddo un eneth a anwyd yn unig,
A hi 'nol yr hanes oedd aeres ei thad.
Aeth cariad i'w gweled, yn l^an a phur lencyn,
Ond codai'r ysgweiar yn araf ac erch,
I saethu'r bachgenyn, ond gwyrodd ei linyn,
A'i ergyd yu wyrgam i fynwes ei ferch.
The Ash Grove
The ash grove how graceful, how plainly tis speaking,
The wind through it playing has language for me;
When over its branches the sunlight is breaking,
A host of kind faces are gazing on me.
The friends of my childhood again are before me,
Each step wakes a mem'ry, as freely I roam,
With soft whispers laden, its leaves rustle o'er me,
The ash grove, the ash grove, alone is my home.