AQ. [sr] became [ss]; [sr] > [ss]
Tolkien described several phonetic developments for the Quenya combination sr in the history of the language. He described essentially the same phonetic developments in both the Outline of Phonetic Development [OP1] from the 1930s and the Outline of Phonology [OP2] from the 1950s:
While s was still voiceless sr > sř > ss (similar to developments after stops) ... Later forms have zar (OP1: PE19/49).
In that case there are three developments of sr: (a) oldest, while s remained voiceless, sr > sř > ss: this commonly survived, being sufficiently perspicuous etymologically, in PQ and TQ; (b) after the voicing of intervocalic s > z, sr > zr > rr (such forms were more frequent in Ñ[oldorin] dialect, since z itself had there become r); in late formations z-r > zar (OP2: PE19/102).
The “intermediate” sound change (sr > zr > rr) appears in the first draft of a table of medial developments in the 1930s (OP1: PE19/52 note #119), but this page was rejected and the phonetic development does not appear in the final table, although sr > ss does (OP1: PE19/51). It seems the series of three distinct sound changes for sr was restored in the 1950s.
The first of these sound changes (sr > sř > ss) probably belonged to the Ancient Quenya period. Despite the supposed “survival” of this ancient sound change, I can find no examples of it in the phonetic history of individual words, where the intermediate voicing change of sr > zr > rr is more prevalent:
Thus, the ancient sound change of sr > ss was either frequently reformed, or Tolkien abandoned this phonetic development when forming actual words.
Conceptual Development: The one clear example of sr development in Early Qenya also shows sr > rr:
Neo-Quenya: For purposes of Neo-Quenya, I think it best to ignore this ancient change and assume that sr > zr > rr was the normal development, as described in the entry on how [z] and [ð] assimilated to following [r], [l].
Reference ✧ PE19/102
|Before||04500||medial [s] often became [z]|
Phonetic Rule Elements
||✧ PE19/102 (sr > sř > ss)|