--- In phoNet@yahoogroups.com, "Jean-Paul G. POTET" <potetjp@w...>

> If [N] were a phoneme in English how is it that this sound only
occurs before /g/, /k/ or in a final position?

Because it was an allophone of /n/ before final [Ng] was simplified
to [N], presumably related to the reduction of final [mb] to [m] (as
in 'lamb') and vacillation in the reduction of final [nd], which
allowed 'parasitic' [d] as in English _sound_ from Old French from
Latin _sonus_.

After the fall of [g], which has not happened everywhere, there is
the contrast 'sin' v. 'sing', so [N] is now in a phoneme of its
own, /N/. Once 'singing' becomes [sIN.IN] it is securer, and more so
once that gets syllabified as [sI.NIN].

Which nasal we have in words like 'income' and 'ink' is another
matter, and I suspect only matters if you want to sound like a native.