From, "Welsh and English Hymns and Anthems" of The Welsh National Gymanfa Ganu Association, Inc. (from the U.S.A.):
The Alphabet - Y Wyddor
A Guide to Pronunciation
A B C CH D DD E F FF G NG H I L LL M N O P PH R S T TH U W Y
The accent in Welsh Words is nearly always on next to the last syllable, except in a few instances when it falls on the last syllable.
There are no silent letters in Welsh Words, and the same letter has nearly always the same sound.
A - short as in "man", or long as in "half". Never as in "mane".
B - as in English.
C - as in "can"; never as in "city".
CH - a guttural sound as in Scotch word "loch", much emphasized; never sounded as in the word "church".
D - as in English.
DD - has the sound of "th" in "this" or in "heather"; never as the "th" in "smith" or "earth".
E - as in "men", or as "a" in "lady".
F - As in "of", or as "v" in "ever".
FF - as "f" in "for" or "ff" in "effort"
G - always hard as "g" in "egg", never soft as "g" in "gin".
NG - nasal as in "ring"
H - always aspirated as in "hard".
I - short as "i" in "win", or long as "ee" in "queen".
L - as in English
LL - has no equivalent sound in English, but is pronounced by placing the tip of the tongue at the back of the top teeth, and forcing out the breath on both sides of the tongue.
M - as in English.
N - as in English.
O - short as "o" in "not" or long as "o" in "rose".
P - as in English.
PH - as "ph" in "physics"; same sound as the Welsh "ff".
R - always trilled as "rr" in "arrow", or "r" in the French word "pere".
S - as in "sin"; never as in things.
T - as in English.
TH - as in "thin".
U - as the "y" in the English word "hymn".
W - as "oo" in "fool".
Y - as "u" in "run"; when occuring in the last syllable of words of more than one syllable and followed by a vowel, it is sounded like the "y" in "hymn".
- The only consonants which are doubled in Welsh are N and R.
- The letters J K V X and Z never occur in purely Welsh Words.