IF MR. James Joyce were to return to Dublin today and if Mr. Leopold Bloom were to come back and make his famous journey through the city as he did on the first "Bloomsday" in 1904, they would both find great changes indeed. Being the kind of persons they were, they would certainly notice very quickly the change in musical taste and the changing face of the Dublin pubs; and, in our day, music and pubs are not unconnected subjects.