Music: A Musical Summer Guide to Europe

June in Europe marks not only the opening of the sightseeing season, but also the annual recurrence of festival fever. This summer U.S. tourists will find more than 50 music festivals to choose from. There are the usual flying squads of big-name soloists, concert-hopping on split-week schedules, and the customary local specialties. The dominant flavor this year is contemporary, with a spate of premieres scheduled. Among the top attractions:

Prague (May 12-June 3). Now in its 15th year, it remains the only Eastern European festival as lavish as its Western counterparts. Highlights of its month-long program: Mikhail Glinka's Russian and Ludmilla, a less well-known but far better work than Glinka's only other opera, A Life for the Tsar, Gustav Mahler's massive oratorio, Das Lied von der Erde. to be played in the ancient Gothic St. Vitus Cathedral; the first performance outside Russia of Dmitry Shostakovich's new Concerto lor Violoncello.

Florence (May to-June 30). Celebrates the 200th anniversary of Florentine Composer Luigi Cherubini's birth with the first modern performance of his long-forgotten Elisa. The Maggio Musicale will also offer a handful of 20th century works, including Janacek's Jenufa, will feature concerts by Milan's Nuovo Quartette, the Philharmonic Orchestra of Warsaw, Violinist Isaac Stern.

Brussels (May 2-June 23). An International Festival that relies almost entirely on visiting troupes, including Britain's Royal Opera in a production of John Gardner's The Moon and Sixpence, the Bolshoi Ballet, the Little Ballet Troupe of Bombay and the 360-member Sofia Opera, which will present the first Western stage performance of Prokofiev's War and Peace.

£ausanne (May 25-June 22). Now in its sixth year, it is Western Europe's best showcase for little-known Communist talent. Among this year's visitors: the 250-member Belgrade Opera (in Mussorgsky's Boris Godunov and Kho-vantchina, Tchaikovsky's Eugen Onegin), the Budapest Ballet, the Warsaw Symphony.

Spoleto (June 8-July 10). Gian Carlo Menotti's Festival of Two Worlds rounds into its third year with its finances noticeably sagging but its programing as lively as ever. The opener is a new production of La Boheme, directed by Menotti and conducted by Thomas Schippers. Also on the program: three works by the newly formed Spoleto ballet company, Cherubini's rarely heard Missa Solemnis.

Gologne (June 10-19). The most ambitious of contemporary music festivals offers 16 world premieres by such avant-garde composers as Mauricio Kagel, Herbert Eimert, Pierre Boulez, Wolfgang Fortner, Karl Blomdahl and Karl-heinz Stockhausen, whose Contest Between Electronic Sound and Instruments is expected to be the festival's most impressive explosion of sound.

Aldeburgh (June11-26). In a bleak antique setting, this remains the most determinedly regional of European festivals. Founded by Benjamin Britten, it has been the site of numerous Britten premieres, will this summer offer his new full-length opera, Midsummer Night's Dream.