HOVERING HELICOPTER : TILSON THOMAS STRIKES A NEW NOTE AT BOWL

Harassed by a single but noisy helicopter in the quiet opening section of Part II of Gustav Mahler’s gargantuan Symphony No. 8, Tuesday night, Michael Tilson Thomas did not glower, or curse the skies, as some other conductors have done at Hollywood Bowl.

He didn’t halt the performance and give a speech, He didn’t stop and wait for the intrusion to end.

He simply left the stage.

It was a dramatic gesture, coming as it did nearly a quarter-hour into the hourlong second movement. And it interrupted proceedings in which some 450 other musicians were involved on the stage, with an audience of 9,804 looking on.

But, when Tilson Thomas resumed the performance, nearly half an hour later, he did so with renewed concentration and an even greater sense of purpose than he had shown, earlier.

(An official at the Los Angeles Philharmonic Assn. told The Times Wednesday morning that the offending helicopter was a police vehicle in pursuit of a suspect.

(Also Wednesday, Tilson Thomas himself explained that, “when I realized that it (the helicopter) wasn’t going to go away, I just had to stop. Thank goodness (Philharmonic general manager) Robert Harth was able to get on the phone and relieve the situation. Usually, we the performers are able to tune those noises out. This time, I had had enough.”)

Actually, the performance proved to be one of Tilson Thomas’ finest and most faceted achievements on this podium.

The combined L.A. Philharmonic and Philharmonic Institute Orchestra made mighty, but seldom raucous, sounds in the overblown “Veni, Creator Spiritus” movement, even more mellow, powerful and detailed musical expressions in Part II.

The L.A. Master Chorale, Pacific Chorale and San Francisco Boys Chorus--the total contingent also including members of the Choral Society of Southern California and the San Diego Master Chorale--produced handsome and edgeless vocalism and delivered the texts with greater clarity than the singing soloists.

Those eight singers, who were Phyllis Bryn-Julson, Roberta Alexander, Marvis Martin, Ruby Hinds, Janice Taylor, George Gray, Dale Duesing and Willard White, though they displayed graphically in some moments the strains caused by Mahler’s often unflattering and unidiomatic vocal lines, still coped bravely and effectively with them. At least at mid-range; above the staff, only one of these singers seemed comfortable.

That was Marvis Martin, who from the light tower overlooking the shell sang the “Mater Gloriosa” portion of the finale with gorgeous tone, wonderful (if incomplete) control and a projection of spirituality her fellow soloists failed to match.

Before and after that special moment, both light towers hosted instrumental ensembles at crucial points in the performance. That Tilson Thomas integrated all these extramusical elements within a reading of purposeful textual connections and apprehendable architectonic continuity is tribute to his powerful and irresistible musical mind. Those who predicted long ago the steady development and eventual triumph of that mind can now be very proud, indeed.