mutation and rinya

Hello all.

I'm currently working on the definite article for Rinya, and it seems
that the initial sound of the noun undergoes some sort of mutation=20
after the article (and what is a poor conlanger to do but to obey
his conlang). The definite article is 'in'. Example:

(i)   in deloth > in deloth
(ii)  in bacor > im bacor
(iii) in cwol > ing gwol=20

({c} =3D /k/. So now you know where I stand in that discussion :)

in > im is ordinary assimilation, but what happens in (iii) /k/ > /g/?
What exactly is the difference between lenition, soft mutation,
nasal mutation (the Pinocchio syndrome :) and any other sort
of mutation?

Nasal mutation seems to have something to do with a final
-n (and other nasals) and its influence on the following consonant.
The only source I've found on nasal mutation is Sindarin and there
/n/ + /k/ becomes /n/ + /x/, ie. /k/ "softens" to /x/.
/k/ becoming its voiced counterpart /g/ seems rather to be called
lenition.

I'm feeling somewhat confused here. Someone feel like helping
me out, please?

Daniel Andreasson

PS. It looks like I'm finally working enough on one project to
actually call it a language. Hopefully it will be on the web within
a couple of weeks. Because then uni starts and taking both
Linguistics 102 and The history of the nordic languages 101
will probably leave little time for conlanging...