S. final [rr] became [r]; [-rr] > [-r]

Based on a single example, it seems that long final [rr] became single [r] in Noldorin:

S. voiceless nasals were voiced; [m̥|n̥] > [m|n]

Anatoly Liberman posted this very interesting article on the etymology of the English word dream, and it got me thinking whether Tolkien was aware of the ambiguity behind the etymology (in Old English, the word seems more associated with "joy, noise, life" than "dream", it's worth reading the entire two-part article) and made the roots OLOS and GALAS similar on purpose. I am probably seeing stuff into things here, but I wouldn't put anything past Tolkien :)

S. short vowels generally lengthened in monosyllables; [C*V̆C] > [C*V̄C]

NOTE: The examples in this entry were fairly comprehensive when it was written (April 2019) but new examples may have been published since then. For brevity, this entry does not provide references for every word, but it does link each to the appropriate word in Eldamo.

S. final [w] usually became [u]; [-C{vw}|-aw] > [-Cu|-au]

In both Sindarin and Noldorin, where it was not otherwise lost, a final [w] usually became [u], mostly notably after a consonant as described by David Salo (GS/§4.195). In Tolkien’s writing, he sometimes represented this final [u] as -w, but this seems to be an orthographic convention, not the actual pronunciation. He mentioned this sound change a number of times:

S. final [vn] sometimes became [von]; [-C{vw}|-aw] > [-Cu|-au]

In Noldorin, there are several examples where a final [-vn] became [-von]:

S. final [l], [r] usually became syllabic; [-C{lr}] > [-Co{lr}]

In both Sindarin and Noldorin, a final [l] or [r] after a consonant usually became syllabic, and developed into [-ol] and [-or] respectively, as noted by David Salo (GS/§4.192). There are a large number examples in both Sindarin and Noldorin:

S. long voiceless spirants shortened; [θθ|xx] > [θ|x]

In both Sindarin and Noldorin, long voiceless spirants shortened, as noted by David Salo (GS/§4.184). Tolkien alluded to this phonetic development in a discussion of the transcriptions used by Ælfwine in his document on the Feanorian Alphabet from the 1930s:

S. [h] vanished after vowels; [Vh] > [Vø]

In both Sindarin and Noldorin, any non-initial [h] vanished after vowels, as noted by David Salo (GS/§4.100, GS/§4.107, GS/§4.116). A similar sound change occurred in Welsh (WGCH/§94ii). This sound change primarily applied to the [h] that developed from intervocalic [s] which therefore ultimately vanished, as described by Tolkien in a note in The Etymologies from the 1930s: