For a conductor blessed with good health, turning 70 is hardly tantamount to retiring. A number of celebrated maestros achieved many of their greatest successes after reaching that age — think of Georg Solti, Leopold Stokowski, Pierre Monteux and Pierre Boulez, who turned an amazingly vital 75 this year.

Last March Lorin Maazel joined that elite of podium seventysomethings. He is celebrating his birthday by guest conducting major orchestras, including, this weekend, the Chicago Symphony Orchestra.

He is one of a handful of virtuoso conductors on a depleted global scene, and it was good to have him back at Orchestra Hall Thursday after a 10-year absence.

I heard numerous Maazel concerts with the Cleveland Orchestra during the 1970s when he served as that ensemble's music director. I found him distressingly uneven — inspired one moment, mannered the next — although he was a marvel with the baton and could elicit some exquisite playing from the band that George Szell had built.

He did so again with the CSO on Thursday, and the mastery was unmarred by mannerism. His beat and gestures were a textbook model of clarity, the intentions behind them equally lucid. There was no mistaking the firmness or flexibility of his command, or the intensity of the orchestra's response.

Maazel revisited an old specialty he had directed at his CSO subscription series debut in 1973, the Sibelius Symphony No. 2. He also revealed a side of himself few listeners are aware of — Maazel the composer — by leading the U.S. premiere of his own "Farewells," Symphonic Movement (1999).

Scored for large orchestra with a huge percussion battery, "Farewells" may be the first apocalyptic music of the new century. In his detailed program note, Maazel writes of his pessimism about "obtuse" mankind's chances of survival on a planet that is rapidly being despoiled. At various times in the 27-minute work his music graphically depicts the "inhuman crunching" of our machines in a sardonic pandemonium. A whimper of piccolo is beaten down by the din, only to reappear faintly at the end. A quartet of Wagner tubas briefly soothes the existential despair.

Despite its angry blasts of dissonance, "Farewells" clings to the moorings of diatonic tonal harmony. Maazel is a skilled orchestrator who writes with obvious craft in an eclectic style. The music went over well with the audience; this listener heard impressive things but also a lot of what could have passed for a superior brand of film music. And the composer's use of siren, whistle and lion's roar seemed a bit naove compared with what Edgard Varese did with them in his "Ameriques," which the CSO played here only a month or so ago.

Maazel's approach to Berlioz's "Roman Carnival Overture" deconstructed the work and lovingly put it back together as a tone poem.

The Sibelius symphonies don't turn up nearly so often on concert programs as they used to, perhaps because we don't have interpreters of Maazel's stature to bring them to such brilliant life as he did with the Sibelius Second.

String lines were eloquently molded, the dark brass pronouncements splendidly defined within a cumulative sweep of sound that honored both structure and atmosphere. Tempo adjustments were handled so smoothly one was hardly aware that any musical gear shifts were being made.

In the right hands, this symphony cannot fail to excite orchestras and audiences, and it certainly did so on this occasion.

The program will be repeated at 8 p.m. Saturday. Phone: 312-294-3000.