This Ilkorin phonetic rule is similar to sound changes that occurred in Old Noldorin. The clearest examples of this rule are ᴹ✶kyel(e)p[e] > Ilk. telf (Ety/KYELEP), ᴹ✶b’rittē > Ilk. brith [briθ] (Ety/BIRÍT), ᴹ✶alkwā > Ilk. alch [alx] (Ety/ÁLAK), and ᴹ✶orku [?urku] > Dor. urch [urx] (Ety/ÓROK). It is possible that the voiceless stops first became aspirates [pʰ], [tʰ] and [kʰ] and then these aspirates became voiceless spirants [f], [θ] (= “th”) and [x] (= “ch”).

In the case of pairs of stops, it seems likely that both stops developed into spirants, but this change is obscured because the resulting double spirants became single. In the case of [kt], it seems the development was to [xθ] and then [θ], for example: ᴹ✶oktā > [oxθa >] Ilk. oth (Ety/OKTĀ).

Based on the examples Ilk. rant and Ilk. Thorntor, it seems that this change did not occur after nasals, unlike Old Noldorin. Another aberrant form is tolda- < ᴹ✶tultā-, where the [lt] became [ld] instead of [lθ], though there is no clear reason why this happened. Helge Fauskanger suggested that perhaps [lt] became [ld] very early, and [l] + [t] only became [lθ] in later compounds like Balthor (AL-Ilkorin/tolda).