ANTHONY BURGESS, the novelist, has written a musical, ''The Blooms of Dublin,'' based on ''Ulysses.''

By ANTHONY BURGESS
If you drive North from Venice you will eventually come to Trieste. It has, because of its history, acquired a non-Italian aura to those who have merely heard about it or noted its position on the map, but, entering it, you will have no sensation of leaving Italy. There will be copies of Telegiornale and Cinzano and Campari in the bars, Agip garages and the confections of Motta. Address the Triestines in Italian, meaning the version of the mother tongue used on the radio or television, and they will understand you, though their version of Latin has an X in it, and they turn the Latin H into a G. The letter survives from young Lucia Joyce to her father James, beginning ''Go una bella balla'' - ''I have a lovely ball'' - and that ''go,'' which is ''ho'' on radio and television, is a typical Slav mutation. Trieste is partly a Slav-speaking town, which is why the neighboring Slavs of Yugoslavia have wanted it for their own.

You will see plenty of blonds and redheads around, as in the Venice of the Titian who glorified auburn tresses, and you will find, in some of the cafes, newspapers attached along their spines to tough wooden laths, as in the coffee houses of Vienna. There are odd hints, though not many, that this city once belonged to the Austro-Hungarian Empire. As for James Joyce, you will find his stay celebrated in a street named for him - Viale Joyce. There's also a street named for the great Triestine novelist Italo Svevo, whom Joyce discovered and persuaded to publish. His best novel is ''Senilita,'' made into a fine Italian film, and Joyce provided the English title -''As a Man Grows Older.''
When Joyce left Dublin in 1904 with Nora Barnacle, the uneducated Galway girl who bore his children and belatedly became his wife, he went first to Pola, which was then in Austria. It is now called Pulj and is in Yugoslavia. When Pola became suspicious of foreigners, Joyce moved from the Berlitz School there, where he taught English, to the sister establishment in Trieste, which was also in Austria. He liked the place, which was a kind of Adriatic Dublin, only bigger. It was the chief seaport of Austria-Hungary, with its mouth open for the engorging of oriental trade. He found his English-language pupils chiefly among naval officers.



Being full of sailors, Trieste was a convivial town, and Joyce drank more than he earned. It was full of Jews, who were more welco methere than in other cities of the empire, and Joyce was able to dreamup a Leopold Bloom, the father-seeking-a-son of ''Ulysses,'' with an authentic Jew ish background - difficult to do in Dublin, where the Jewish popula tion was small (according to Mr. Deasy, in ''Ulysses,'' it is nonexis tent). Leopold Bloom is more a Triestine figure than a Dublin one.
It is useless to go tirelessly around Trieste seeking out the taverns from which Joyce emerged drunk and incapable, often spending the night in the gutter. He was in all of them, but some of them are no longer there. His various lodgings are still around - 3 Piazza Ponterosso, 31 Via San Nicolo, 1 Via Giovanni Boccaccio - or were when I was last in Trieste. More important are the ever-living landmarks which Joyce saw - the terraced slopes which start at the sea and climb toward the hills; the Citta Vecchia, or Old City, dominated by the Romanesque Cathedral of San Giusto (whose feast day, Nov. 2, Joyce remembered all his life); the new town, built on land reclaimed from the Gulf of Trieste by the Emperor Joseph II in the 18th century, handsome with wide streets and spacious buildings. Outside the city are the ruins of the Castle of Duino, to which it is believed Dante paid a visit, and the modern castle where Rainer Maria Rilke wrote the ''Duino Elegien.'' Closer to the city than Duino is the castle of Miramare, built by the Archduke Maximilian before he went to Mexico to die before a firing squad in 1867.



In Joyce's day, there was a powerful nationalist movement among the Italian-speaking Triestines which almost exactly paralleled the situation of the Irish. This made Joyce feel at home. It is the strong Italian-speaking element of the city which has prevailed against history's long efforts to make Trieste French, Illyrian, Austrian and, at the end of World War II, a p rovince of Tito's Yugoslavia. In 1947 Trieste became briefly an independent state - a Mickey Mouse state or stato Topolino, as the Italians called it. American and British troops held the zone aga inst the threat of Tito's tanks. Now the territory is indubitabl y part of the Italian motherland, and the Yugoslavs seem to sulk ab out it. Yugoslavs are, historically, all children of Venice - the li on of St. Mark is embossed on all the stonework of the coast - but they pretend to have forgotten their Latin inheritance. When you drive across the frontier, the customs men will say: ''Alles i n Ordnung?'' - preferring German to either Triestine or Vene tian.

Trieste has lost its old grandeur as a port. It no longer serves the commerce of a great empire, and it may be regarded as the torpid terminus of free Europe. Still, there are always ships in the harbor, as well as a new brand of foreign sailors - chiefly Indians and Pakistanis. But the wealth of the commercial city draws increasingly on the Italian hinterlands.

The shops are smart and busy, the people well dressed and lively. The restaurants serve fine Adriatic fish -far superior to what you'd get out of the Mediterranean and second, perhaps, only to the fish of the North Atlantic. The aquarium, with its pet penguin Marco, is one of the finest in Europe. If you're looking for the charm of Florence or Siena or the baroque magnificence of Rome, you will not find them there - in respect of the lack of architectural interest you may dub the city ''Non-Italian.'' But ''Italian'' has little true meaning and may not be used as an analogue of ''American,'' which has a true meaning. Trieste is itself as Venice is itself and Bolzano, where they speak German, is itself. National unity is a political fiction in Italy. The town is characterized more by warehouses and insurance offices than baroque churches and statuary. The young women are mostly exquisite, Titianesque without Titian opulence. There is chic and animation and no lack of lively talk. The drunkenness is mostly an importation of the sailors.
T hough both Joyce and his master Henry Ibsen first met the South here, that tolerant softness that tempered their natural rigor, the North is ever-present in a turbulent wind called the Bora (derived from the Latin Boreas which we read of in the Roman poets). With polar ferocity this great wind rages through the streets in winter and knocks one over. In summer it scarcely mitigates the huge heat. Joyce knew it, and we can still visualize his lanky underfed frame wrestling with its rude strength.
If we mostly visit Trieste to see the environment where Joyce wrestled with the first chapters of ''Ulysses'' and Svevo completed ''Senilita,'' we would be unwise to view those two great novelists as solitary sports in a city not much given to the arts. Both Joyce and Svevo were more citizens of an empire than of a mere city. The Austro-Hungarian empire produced great art, from Haydn and Mozart through Beethoven to Richard Strauss, from Metastasio to Rilke and Hofmannsthal. And ''Ulysses,'' though completed and published in Paris, is a product of that huge culture whose center was Vienna but whose extremities touched the Adriatic. ''Ulysses'' may be about Ireland, but only turbulent and cosmopolitan Trieste could have given Joyce the impetus to start setting it down.
Illustrations: photo of Piazza della Borsa map of area of Trieste