There were Friday night sessions in the Kitchen Bar in Belfast City Centre, but last I heard the whole pub was being moved due to redevelopment. The John Hewitt (in the "Cathedral Quarter" of the city) apparently has music.

There was a thread on this last year, and I'm sure there's listings somewhere online - I'll have a dig around.

And if you fancy going further down the coast at all, my ma and da would be only too happy to give you a bed for the night and point you in the direction of the good pubs!