Milestone for Maestro Solti - Chicago style. The city has just thrown Sir Georg a week-long birthday party culminating in a gala concert that brought out an elegant audience and lots of warm feelings for the revered conductor.

Banners festooned the light poles on Michigan Avenue, wishing Sir Georg ``Happy Birthday.'' It was ``Sir Georg Solti Week'' in Chicago, by mayoral decree. But the entire series of events was as much a compliment to the city of Chicago, as it was to Sir Georg (pronounced ``George'' ever since he was knighted) - the conductor who restored the Chicago Symphony Orchestra's luster and catapulted it into superstar status.

I say a compliment because it's hard for me to imagine this sort of outburst of civic attention and pride happening in New York, for example.

Gov. James R. Thompson appointed Solti Illinois's cultural ambassador. Mayor Harold Washington gave Solti the Civic Medal of Merit during the intermission of the concert. As its final gesture, the city unveiled a bust of the maestro just to the left of the beautiful Lincoln Park Conservatory.

The main focus of the event, however, was the concert, in which Solti was a major participant. He even played the piano - something he hasn't done in public for years and had been promising to do for well over a decade. (That concert raised over $300,000 for the orchestra.)

Now ``gala'' concerts are the sort of events that promise more than they deliver, and it would be misleading to say that this birthday concert was an unforgettable musical experience. But it would be equally wrong to imply that it wasn't fun, because it was - immense fun. First there was an elegant audience. Then there was the Orchestra Hall auditorium itself, hung with gorgeous red, orange, and burgundy flower garlands, the stage rimmed with a festive line of red tulips. Even the television cameras added a curious sense of excitement - proof that parts of the evening were being taped for airing on the Public Broadcasting Service, Dec. 28.

Composer-in-residence John Corigliano got things off to an engaging start with his specially commissioned ``Campagne di Ravello'' (``Bells of Ravello'') - a short piece that crossed Respighi, Mussorgsky, and Copland, while interweaving ``Happy Birthday to You.'' It built to a boisterous climax and was quickly, and colorfully, over. There followed a ``Fledermaus Overture'' with the conducting tenor Pl'acido Domingo on the podium.

Then Solti appeared, after an interminable setup to get two pianos on stage and organize the TV cameras and personnel. Fifteen years ago, an audience would have leaped to its feet to welcome the honoree who has reestablished Chicago as one of the finest orchestral cities of the world. Then again, Chicagoans can be a surprisingly undemonstrative lot, and on the basis of this evening, I can fully understand why Solti loves coming to New York, where the ovations are almost frightening in their noise and intensity.

Solti's vehicle for his return to the keyboard was Mozart's Two-Piano Concerto in E flat, K. 365. His partner was Murray Perahia, who has guaranteed his nook in music history with his recorded cycle of the Mozart concertos on CBS Masterworks. Seated at the keyboard, back to the audience, arms seeming to reach to each side of the stage, twitching and jabbing in his unique fashion, Solti seemed mightily uncomfortable during the introduction, but once the fingers hit the ivories, he gained his poise anew. The performance was nothing exceptional, but it hardly mattered. He had returned to the keyboard here in Chicago and his admirers were delighted to be a part of the historic experience.

After the intermission and the presentation of the Medal of Merit, Solti led his masterly band in a reading of Strauss's ``Don Juan,'' which may not have been particularly clean in matters of ensemble but was remarkable in terms of mellowness, warmth, and those special moments of lustrous tonal splendor that we have come to expect from this magnificent ensemble.

The evening closed with scenes from the first act of Verdi's ``Otello,'' long a Solti favorite. Mr. Domingo sang Otello's music and Kiri Te Kanawa was the Desdemona. The Chicago Symphony Choir was on hand, as well. But the selections belonged to maestro and orchestra. The moments of true beauty and poetry that Solti elicited were something to treasure.

The subscription concert program that was also heard that weekendtold more about the orchestra and Solti's increasing mellowing as a music director. Ensemble is no longer the inexorable priority it once was. Nowadays, one hears that sense of relaxation in both the playing and the musicmaking that has been increasingly a part of Solti's profile.

The concert got off to a delicate start with Haydn's second Organ Concerto in C (Hob. XVIII:8), fleetly played by David Schrader. The same composer's 93rd Symphony (D major) had the sort of wit one does not hear too often from Solti, and all the players seemed to be enjoying his way with the music.

The second half offered both Mozart's ``Die Zauberfl"ote'' Overture and his Prague Symphony (No. 38 in D, K. 504). The ``Flute'' overture bubbled with mystery and joy; the ``Prague'' was elegant, eloquent, and often sumptuous to listen to.

And now Solti, who once said that Chicago ought to raise a monument to him, will now be immortalized in lakeside Lincoln Park. Ironically, Dame Elizabeth Frink's eight-foot-high bronze bust captures the subject in his severest glaring mode. The Solti seen all last weekend was a smiling, happy, nimble man who was jumping off the second step of his podium, shaking everyone's hands, and generally enjoying all this outpouring of love. That's the vision of Solti most of us there will treasure.