Extra-musical aspects of Anna Netrebko's her memorable, at times brilliant, recital last night in Herbst Theater raised questions about just when this explosively talented young soprano will start acting her age, and focus more on the music and the audience. Dripping charm and creating havoc, Netrebko played the diva, toyed with the audience, confused her accompanist, preened, giggled and exhibited a happy, single-minded preoccupation with herself. It's not a long way from the "act" (if that's what it is) to diminished sincerity and integrity in the interpretation of the music. The show became more important than the concert. It was one thing for a 22-year-old almost a decade ago to make a dizzy and dizzying US debut in the Kirov's "Ruslan and Lyudmila" in San Francisco, and quite another to carry on the foolishness into the beginning of her mid-career period. The San Francisco Performances concert was twice postponed by the singer. There was a printed program, an updated program replacing the original one, and Netrebko then changed the selections as she went along - at times, but not always, in consultation with Donald Runnicles at the piano. In the middle of a set of Rachmaninoff songs (the strongest part of the concert), the soprano left the stage for a quick break, leaving Runnicles and the audience confused. Her dazzling outfits for the recital (a Carmen-Miranda floral dream and a form-fitting black ruffled creation with oversized jewelry) were prepared with much more care than the program. And, although bathing her admirers in high-voltage smile throughout, the singer was less than generous with the audience. With about an hour of music, a late start, and a long intermission, Netrebko gave two brief encores ("O Mio Babbino Caro" and Bizet's "Les Filles des Cadix.") Now for the good news: the silvery, agile, small voice has deepened, broadened, gained strength and punch. The Rachmaninoff songs - especially "Never Sing to Me Again" and "Discord" - were powerful and spectacular, although the effort to maintain physical drama took away from the impact of the performance. When you watch just how long the singer will maintain a fully stretched pose of being carried away, it's just more difficult to be carried away by the music, however well sung. The same over-dramatization interfered slightly in Ilia's aria from "Idomeneo," but the performance was musically superb. Less effective was the Mozart concert aria "Per pieta, bell'idol mio," music without large gestures that seem to inspire the singer. Surprisingly, Netrebko started a set of six songs by Richard Strauss with the traditional "closer" or encore item, "Zueignung," delivered a funereal "Morgen," but singing a beautiful, true lullaby in "Wiegenlied," getting into a bit of pitch problem in the middle of "Cacilie," but then singing hell out of the song's big, showy climax. Runnicles played beautifully throughout the short and confusing evening, kept in the background, had to be dragged out to take a bow, behaved as an indulgent mentor or even father would. Perhaps a bit of tough love would have been more in order. Janos Gereben/SF www.sfcv.org [log in to unmask]