Returning a RECORD, not SETOF RECORD

I just discovered that my previous post concerning this had the same
subject line as a discussion that took place in January. I'm not asking
the same question though, so here I go again with my question about
syntax and feasibility.

I do the following:

CREATE FUNCTION xyz(int, int) RETURNS RECORD AS '...'
CREATE TABLE abc(a int, b int);

Now I want to call my xyz function once for each row in abc and I want
my RECORD to be (x int, y int, z timestamptz). How do I write that
query? I.e. where do specify my RECORD definition? Is it possible at
all? Ideally I'd like to write something like this:

SELECT xyz(a, b) AS (x int, y int, z timestamptz) FROM abc;

but that yields a syntax error.

Regards,
Thomas Hallgren