If you judge instrumentalists by their best work, the Australian Chamber Orchestra is terrific. If your top consideration is consistency, this group of young, standing, conductorless musicians is more fair-to-middling - at least, according to tonight's experience. At this ACO concert, in Herbst Theater, there were two remarkable second movements and an impressive performance of Peter Sculthorpe's 1988 String Sonata No. 2. Led by its longtime (although still youthful-looking) artistic director, Richard Tognetti, the ACO ripped into the Allegro of Haydn's Symphony No. 49, fully justifying its nickname, "La passione." Too many Haydn performances are bloodlessly "classical" and this lively, committed approach proved once again how much life there is in Papa. Another high point came in the second movement of Bartok's Divertimento for Strings. The dark, slowly-moving night music came across exactly right - strangely mirroring Sculthorpe "desert music." The long, frightening crescendo/decrescendo in the Bartok, the percussive attacks in the String Sonata (an interesting, enjoyable, but not exceptional work) spoke very well of the ACO. It was a different story with the rest of the Haydn (competent, but no more), the two outer movements of the Bartok, and the entire Mozart Piano Concerto No. 9. It sounded like an off night for the soloist, Stephen Hough, whose solo recital with San Francisco Performances three years ago was often dazzling. This time, it was note after note, all in order and not much to write home about. Hough and the orchestra went on autopilot and stayed there. Mozart deserves better. Tognetti's band tried harder in the Divertimento, but except for the middle movement, came up short. The challenge, to be fair, is enormous. In both outside movements, there are "unplayable" contrasts - between forceful and dancing figures, between strong and playful themes - and the ACO chose (or was limited to) the middle path, not doing justice to either extreme. As if to prove that it has a problem with "gritty music," the orchestra offered a Piazzolla Boliviana as encore, one of the very few pieces from this Bartokian master of stark power that sounds like background for afternoon tea on the verandah. ACO is an amazing mix of personalities, from a first cellist who never takes her eyes off the leader, to the second cellist who never looks up from the score. There are expressive faces and those made for poker. Besides Tognetti, clearly a first-class violinist, the most impressive musicians of the orchestra are the violists - and there are no obvious weak links among the string players. No comment about the brass. There is something about the musicians' appearance that must be said. It's fine and dandy to get away from basic black, but to hang an occasional wrinkled purple or red half-slip or wrap over slacks at random doesn't reflect well on this otherwise talented group of musicians. Excellence in communication needs to extend to the visual as well. Janos Gereben/SF [log in to unmask]