In Ilkorin, it seems that [g] developed into a vowel before the nasals [m] and [n], similar to developments in Noldorin, though the vowels that developed in the two languages were different. This rule seems to apply to original primitive [g]: ᴹ✶lugni > Dor. lûn (Ety/LUG², EtyAC/LUG²). It also applied to [g] that developed from [k] before nasals: ᴹ✶takmā > Ilk. taum (Ety/TAK), as well as [g] that developed from [ɣ] before nasals: ᴹ✶kuʒnā > kogna > coun > Ilk. caun (Ety/KUƷ).

The last of these developments makes it difficult to determine when this vocalization occurred. Since primitive [ɣ] fell together with [g] before nasals, the vocalization of [g] could have occurred earlier, before voiced stops spirantalized after vowels. Phonetically, though, it makes more sense for the vocalization to have occurred after spirantalization so that [Vg{mn}] > [Vɣ{mn}] > [Vu{mn}]. However, it is simpler to describe this rule as direct vocalization of [g], which is how the phonetic development is presented here.

The vowel that developed seems to have been [u], such as: ᴹ✶takmā > Ilk. taum (Ety/TAK). Where the result was [ou], this further developed into [au]: ᴹ✶kuʒnā > kogna > coun > Ilk. caun (Ety/KUƷ). Tolkien seems to have been uncertain about the development of [ug{mn}]. At first he seems to have decided that [g] developed into [i]: ᴹ✶lugni > Dor. luin (Ety/LUG²), but then he revised this word to Dor. lûn, making it consistent with the other developments of [g] into [u] (EtyAC/LUG²).

Unlike what happened in Noldorin, there are no examples of this vocalization of [g] occurring in Ilkorin before [l] or [r]. One possible counter-example indicates that such changes did not occur: legol which may have developed from primitive [leklā] (Ety/LEK). If the vocalization rule applied, it could be expected to develop into [legla >] **leul. The evidence is thin enough, though, that it is hard to make a conclusion one way or another.