Sir Georg Solti has announced his decision to step down as conductor of the Chicago Symphony at the end of the 1990-91 season. He will be succeeded by Daniel Barenboim, the pianist and conductor who now heads the Paris Orchestra.

Barenboim will immediately assume the title of music director designate in Chicago, with six weeks' or more of conducting in each of the two remaining seasons before he assumes the directorship. He will also share duties with Sir Georg on the orchestra's 1990 tour to Japan.Barenboim has conducted and recorded with the world's major orchestras. He's a favorite with Chicago audiences and players, having returned to the Chicago Symphony in 12 seasons and made more than 30 recordings with it, including the complete symphonies of Schumann and Bruckner.

Barenboim was recently at the center of a fuss at the Bastille Opera in Paris, where he had been appointed artistic director. He was fired by Pierre Berge, general director of the Paris complex now under construction, which is scheduled to open on July 14. Many of the artists scheduled to appear under Barenboim in Paris have resigned in protest, including conductor Herbert von Karajan of the Berlin Symphony. (Karajan will conduct in Paris during the Bicentennial of the French Revolution this year, but not at the Bastille, he said.)

- THE VAN CLIBURN INTERNATIONAL Piano Competition, scheduled May 27-June 11 in Fort Worth, Texas, already has applications from 214 pianists in 37 countries - the largest number in the contest's 27-year history. These do not include applications from the Soviet Union or the People's Republic of China, which are still to come. The age range is 19-30, with a concentration at 28 and 29 years of age. More than twice as many men as women have been applying. Among novel applicants are a doctor who graduated from a major college of medicine, a Texas TV news anchor, a gymnast who participated in world championships, a competitive shot-put thrower, and a husband-and-wife piano duo.

- OPERA STAR JOSE CARRERAS, restarting his singing career with a European tour after a yearlong struggle against leukemia, says his illness and recovery have brought him a new understanding of life.

Since doctors pronounced him cured, the 42-year-old tenor has devoted much of his renewed energy to setting up a foundation for research into leukemia. He is spending this winter on a fund-raising tour of European cities. Despite harrowing bone marrow transplants, he refused to go under general anethetic, for fear of damaging his vocal cords. He says his voice is unchanged, but rusty.

- THE COMIC OPERA "TARTUFFE" by Kirke Mechem has had 100 performances in its first decade, more than any full-length American opera written in the past 25 years. (It was presented by BYU Music Theater a few years ago.) Central Opera Service says Mechem thus ranks in popularity with the two best-known contemporary opera composers, Gian Carlo Menotti and Carlisle Floyd. Mechem, 63, has more than 150 published works and is one of the few American composers who make a living solely by composing.

- TREE INTERNATIONAL PUBLISHING, the largest country music publisher in the world, has been sold to No. 1 CBS Records for a reported $45 million to $50 million. Long-time Tree owner Buddy Killen, who said nothing would change but the cash flow, would not agree to the merger until all his requirements had been met - staying in Nashville and keeping the name and all employees.

Tree has 40 exclusive songwriters and its own multistory office building. The company has ranked as Billboard Magazine's No. 1 country music publisher for 16 consecutive years. Its catalog of music copyrights includes more than 35,000 songs, including the standards of Willie Nelson, Buck Owens, Merle Haggard, Harlan Howard and Roger Miller. Tree was the last major publishing property in Nashville that had not been acquired. CBS itself was purchased by Sony for a reported $2 billion in late 1987.

- THORN EMI WILL BUY SBK Entertainment World Inc., a major U.S. music publishing company that owns more than 250,000 individual copyrights, mainly of songs commissioned by big U.S. movie producers. American classics like "Blue Moon" and "Singing in the Rain" will thus become British property under terms of a $336 million purchase by the London entertainment conglomerate.

- LUKAS FOSS will leave his post as Brooklyn Philharmonic music director to devote more time to composing. Foss will leave at the end of the 1989-90 season but continue to do some guest conducting with the orchestra, where he has been for 20 years, becoming music director in 1971.

- PRADO MUSEUM PAINTINGS are remarkably well-preserved but obscured by layers of varnish and patches of discolored overpaint. Now more than 8,000 old master paintings commissioned and bought by Spanish kings will get a facelift. The restoration is directed by Britain's John Brealey, one of the world's best restorers, who has worked on Britain's collections and been head of conservation at the Metropolitan Museum of Art.

Brealey made himself very popular in Spain by restoring Velasquez' masterpiece, "Las Meninas." He will have a staff of 16 assistants, all of whom will be cautioned to respect the painter's intentions. "A successful restoration doesn't jump off the wall," Brealey says. "You shouldn't notice the restoration, you should notice the picture."

- HIGH-CLASS TALK SHOWS and news commentary are replacing great blocks of music programming on public radio, a trend that Newhouse critic Byron Belt deplores. He notes that there is a trend against taped broadcasts of opera and symphony. He deplores poor announcing, with incorrect pronunciations and rambling commentary, and commercial "messages." And he warns listeners to be alert and protest "musical garbage" cut to fit into 12 minutes a turn, the supposed attention span of modern Americans.