Ancient Quenya Phonetics P17.5: syllabic initial [s] became [is]

AQ. syllabic initial [s] became [is]; [ṣ-] > [is-]

On rare occasions an initial s before p, t, k became syllabic, producing a preceding vowel i in most cases. Tolkien mentioned this sound change in both the Outline of Phonetic Development [OP1] from the 1930s and the Outline of Phonology [OP2] from the 1950s:

Quenya Phonetics P16: [v] vanished before [u] after vowels

Q. [v] vanished before [u] after vowels; [Vvu] > [Vu]

Where v (or ƀ) appeared before u in Quenya it vanished; it is unclear whether this loss occurred before or after the shift of ꝑ, ƀ > f, v. This sound change is only mentioned in Outline of Phonetic Development [OP1] from the 1930s in a deleted note:

Quenya Phonetics P15: [ɸ], [β] became [f], [v]

Q. [ɸ], [β] became [f], [v]; [ɸ|β] > [f|v]

In Quenya the bilabial spirants ꝑ, ƀ [ɸ, β] (as derived from primitive ph, b) both became labio-dental f, v. These sound changes were mentioned in both the Outline of Phonetic Development [OP1] from the 1930s and the Outline of Phonology [OP2] from the 1950s:

Quenya Phonetics P13: [ae], [ao] generally became [ē], [ō]

Q. [ae], [ao] generally became [ē], [ō]; [ae|ao|ā{ĕŏ}] > [ē|ō|ā]

Quenya did not tolerate the vowel combinations [ae] or [ao], and these generally became [ē] or [ō]. These sound changes explain the somewhat peculiar rule that the genitive form of nouns ending in -a was -o, for example:

Quenya Phonetics P12: [ɣ] from [g] vanished

Q. [ɣ] from [g] vanished; [ɣ] > [ø]

In Quenya when the voiced stop g became spirantal ʒ [ɣ], the resulting spirant generally vanished. This sound change is distinct from the much more ancient vanishing or ʒ (or h) in Primitive Elvish. Tolkien gave essentially the same description of this sound change in both the Outline of Phonetic Development [OP1] from the 1930s and the Outline of Phonology [OP2] from the 1950s, but with more details in OP2:

Quenya Phonetics P11: [w] became [β] initially and between vowels

Q. [w] became [β] initially and between vowels; [w-|VwV|aiw] > [β-|VβV|aiw]

In Quenya an initial or intervocalic w became v. The same basic phonetic developments were discussed in both the Outline of Phonetic Development [OP1] from the 1930s and the Outline of Phonology [OP2] from the 1950s, but the timing and details of the sound changes were not the same. In the 1930s [OP1], this was a fairly recent sound change, occurring in the Tarquesta (TQ) period and possible in Lindarin only [pre-Vanyarin]:

Quenya Phonetics P10: [wo] became [o]

Q. [wo] became [o]; [wo-] > [o-]

Starting in the 1930s, the combination wo sometimes reduced o, but the exact conditions under which this change occurred are unclear. Tolkien gave nearly identical descriptions of this sound change in both the Outline of Phonetic Development [OP1] from the 1930s and the Outline of Phonology [OP2] from the 1950s: