There was some talk here sometime ago about an abc converter using abcm2ps (I believe concertina.net uses the older abc2ps) but I really cant remember what happened to it.

Anyway, I've decided I might as well have a go inspite of a couple of reservations and see what happens - it may come down again... It is at http://www.folkinfo.org/songs/abcconvert.php

Apart from using abcm2ps, it also differs in that it allows transposition and can display the error/warning messages produced by the abc conversion routines which (at least with abcm2ps) can be useful.