San Francisco Symphony marshalled almost half of the apocryphally required thousand for Mahler's Eighth Symphony tonight, and produced as many as 15 glorious minutes during the work's 85-minute duration, but numbers don't tell the story. Sometimes all the ingredients are present for a performance, but it doesn't turn out as well as it should. Consider the assets present in Davies Hall: - Michael Tilson Thomas, well on his way to the title of "one of the top Mahlerians" of our time. - The Symphony, at the closing series of concert in a season that saw the final phase of transformation into a truly major-league orchestra. - Vance George's farewell contribution with the Symphony Chorus, polished to a high shine over the years, and augmented mightily tonight with extra singers, the San Francisco Girls Chorus and the Pacific Boychoir. - A brilliant cast of soloists, not so much big-name stars as singers eminently "right" for their roles: sopranos Marisol Montalvo (Magna Peccatrix), Elza van den Heever (Penitent/Gretchen), Jennifer Welch-Babidge (Mother Gloriosa), mezzos Stephanie Blythe, Elena Manistina, tenor Anthony Dean Griffey, baritone James Johnson, bass Raymond Aceto. Well, then, what is this obvious "but" coming? I wish I could put my finger on "the" problem, but it's not that easy. Except for a few wonderful instances here and there, and an impeccable finale - Montalvo, van den Heever, and the women's chorus whispering "All that is impermanent..." to a powerful (not just loud) climax - the performance simply did not jell, too many obvious shortcoming propping up. With three more performances coming, this "Symphony of a Thousand" will get much better for sure. The first part of this 1907 double cantata, "Veni, creator spiritus," presented most of the problems. Unlike the finale, this was loud, big, noisy. Unlike what is normally expected from George's chorus, diction was awful; between "veni, creator" and the first "Gloria" - a span of 20 minutes - I didn't understand a single word. Unlike MTT's usual consistency, the performance was all over the place: a rickety start, a briefly clean, lucid section, then some bumpety-bump passages, and much huffing and puffing, blowing the walls down. The few purely orchestral passages later on did credit to the orchestra, all sections doing their best, concertmaster Alexander Barantschik, principal violist Yun Je Liu, and principal cellist Michael Grebanier making affecting contributions. Of the singers, the sensation was Montalvo, in her SFS debut. The tiny soprano (with van den Heever towering over her) has an enormous voice, her high notes are heavenly, and she alone sang without a score, exhibiting a complete mastery of the material. Homegrown van den Heever had some wonderful moments, opening her solo with the self-referential "You soar to the heights," her mezzo-tinged soprano doing some marvelous soaring. Blythe's "By the well" shook the house, in a good way. Griffey's gorgeous voice impressed as usual, but at times he was squashed by Mahler or MTT or both, and at the end of an otherwise beautiful "Look up, into the eyes," this lyric tenor simply didn't have the needed helden edge. A correction about who was not using a score: all the kids of the children's choruses sang from the heart, in all meanings of the phrase. Janos Gereben/SF www.sfcv.org [log in to unmask]