Thank you, Berephon and Cleitanious. After looking at Tolkien's writings in the appendices, it seems that the circumflex "û" also demands stress, forming the only possible exception to the stress-falls-on-first-syllable-of-bisyllabic-words-rule. The examples given were Annûn and Amrûm. Is my interpretation of the writings correct? The examples should be stressed as an-NUN and am-RUN?
And is the Sindarin "y" really pronounced as an English short "u"? I had thought it was much closer to a German "ö".
Thanks again. My confusions are gradually fading.
If you see a diacritic, it usually demands stress as it indicates a long vowel (Númenórean, for instance, is NOO-meh-NOHR-ee-ahn.) However, ordinarily the stress falls on the first vowel (in two syllable words) or the next to last vowel in multi-syllable words. In some cases, it falls on the syllable third from the end, as in Gah-LAH-dree-ehl or AH-rah-gohrn.
Y in Sindarin is technically pronounced as the u in the French word lune (which has that weird truncated eu -- almost a short yu -- that no one but a Frenchman can pronounce.) However, as it hardly appears anywhere except at the end of multi-syllable plural words, it usually gets truncated to a short i (as in him), a sound that does not otherwise appear in Sindarin.