Q. initial [ps], [ks] became [ups], [iks]; [ps-|ks-] > [ups-|iks-]

Q. initial [ps], [ks] became [ups], [iks]; [ps-|ks-] > [ups-|iks-]

Late in Tarquesta [TQ] the initial combinations ps-, ks- came to be pronounced ups-, iks-, a sound change described in both the Outline of Phonetic Development [OP1] from the 1930s and the Outline of Phonology [OP2] from the 1950s:

In TQ though the spelling is retained ps, ks initial are commonly rendered by simple s or ps, ks > ups, iks (OP1: PE19/36).
In TQ ups, iks, rare in PQ, became frequent as colloquial renderings of ps-, ks-, unless a closely connected word ending a vowel preceded (OP2: PE19/79).

In the 1930s, these initial clusters sometimes reduced to s-, a phonetic development also mentioned in descriptions of the Feanorian Alphabet from the 1940s, emphasizing this sound change was not reflected in spelling:

The TQ colloquial pronunciation of initial ps, ts, ks as s is never “correctly” represented as 8 (though this occasionally appears) (PE22/45).

There are no obvious examples of these sound changes in Tolkien’s writing, since they are hard to distinguish from the syllabification of initial followed by metathesis: ṣp-, ṣk- > usp-, isk- > ups-, iks- (which probably helped produce these late TQ pronunciations ofß ps-, ks-).

Neo-Quenya: Most Neo-Quenya authors ignore this sound change and retain the spellings ps-, ks- (or x-). The same is true for the entries in Eldamo, where the original spellings are retained. It’s probably best to consider ups-, iks- as optional changes to pronunciation only.

Reference ✧ PE19/79

Order (04100)

After 03500 [sp], [sk] became [ps], [ks]

Related

Phonetic Rule Elements

[ps-] > [ups-]
[ks-] > [iks-]

ᴹQ. initial [ps], [ks] became [s]; [{pk}s-] > [s-]

References ✧ PE19/36; PE22/45

Order (04000)

After 03500 [sp], [sk] became [ps], [ks]

Related

Phonetic Rule Elements

[ps-] > [s-] ✧ PE19/37 (ps > s; initial)
[ks-] > [s-] ✧ PE19/37 (ks > s; initial)
[ts-] > [s-] ✧ PE19/37 (ts > s; initial)