Roman transliteration of Tamil n's

[Srinivasan Pichumani]

        Dental n alveolar n are members of the same phoneme. Only in a
        few cases of contrast within Old Tamil they need to be marked
        separately as n and _n/n'.

How about the very very common term for "I" -  nA_n !!!

A poster (Dorai Sitaram) used this example on soc.culture.tamil
a long while ago to point out the dental/alveolar difference. I
pointed out to him that he may have chosen quite a difficult
example to illustrate this distinction since, it is probably only
a minority of modern, native Tamil speakers who retain the dental/
alveolar distinction in this word.  The initial n almost always
gets alveolarized, based on what I have heard.

However, I have read that in some Tamil dialects, this distinction
is retained even now.  From my interaction with Malayalam speakers,
I think that they wouldn't find the above example hard at all since,
in general, they seem to keep the dental/alveolar n's quite distinct.
[If I try to say nA_n correctly, I sound like a Malayali ;-)))]

        (similar to Midwestern American r). The two r's are: r= alveolar flap or
        single tap; R/_r is an alveolar trill which developed from Proto-Dravidian
        alveolar stop in the intervocalic position. Like Old Tamil,Old Telugu and
        Old Kannada also had two r's but in modern languages there is only one; the
        trill R merged with the flap r. Only Tamil scholars try to distinguish the
        two in reading.

It is interesting that you don't consider Malayalam once again...
in my experience, Malayalis indeed preserve the r/_r distinction
quite clearly... and so do SriLankan Tamils.

-Srini.